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Armored Ship ROLF KRAKE and the War of 1864
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by Eric Nielsen
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On July 1, 1863, the "armored battery" ship ROLF KRAKE was commissioned into the Danish navy. ROLF KRAKE was the first Danish warship to be built essentially of iron, and to carry its main armament in revolving gun turrets, mounted on the hull's center-line.

When she was acquired by the Danish navy, the ROLF KRAKE represented a culmination of the Danish navy's transition from the all-wood, all-sail warship, to the first all-iron, steam-propelled, screw propeller, turret-armed warship in the Danish navy, a technological transition that occurred over a period of forty years, from the date of the Danish navy's acquisition of its first steam warship in 1824.

This article describes the ROLF KRAKE's innovative, precedent-setting design, and the ROLF KRAKE's historically significant - and instructional - operational employment in the German-Danish war of 1864, during which the ROLF KRAKE acted in unique coast defense roles by (1) providing heavy, mobile, seaborne gunfire support to assist the Danish army's defensive operations ashore, against the invading German armies' seaward flank; and (2) performing anti-amphibious patrol work and combat interdiction, in an attempt to contest and defeat a Prussian amphibious invasion of the island of Als.

Armored Battery (Panserbatteriet) Ship ROLF KRAKE
As Denmark had done in her earlier procurement of marine steam engine and iron warship building technologies, Denmark acquired her first essentially all-iron, steam-propelled warship from a foreign source. In doing so, Denmark selected a private shipyard that possessed previous experience in constructing armored warships and marine steam engines. Thus the ROLF KRAKE, an "armored battery" ship as the Danish navy officially classified her, was ordered by the Danish navy from the Scottish firm of R. Napier & Sons in Glasgow, Scotland, on the River Clyde.

The ROLF KRAKE was laid down in Glasgow in 1862, was launched on May 6, 1863, and was commissioned upon her arrival in Copenhagen, on July 1, 1863. Following her commissioning, the ROLF KRAKE engaged in sea trials from 18 July to 20 August, 1863.

ROLF KRAKE's coal-fired steam engine produced 700 horsepower, which provided a maximum speed of 9½ knots - she actually reached 10½ knots on trials.

Model of the Rolf Krake at the Orlogsmuseum in Copenhagen
Model of the Rolf Krake at the Orlogsmuseum in Copenhagen
In addition to her steam engine, ROLF KRAKE, like other early iron steamships, was also provided with auxiliary sail power capability. The generic concern here was in the reliability of early marine steam engines, and the fact that without the availability of auxiliary sail power, a warship could become completely immobilized if its steam engine completely broke down. Therefore, ROLF KRAKE was schooner-rigged, with fore-and-aft sails rigged on three masts.

As built, the ROLF KRAKE was armed with 4 - 68 pdr. (8"), 88 cwt., smoothbore, muzzle-loading cannon, mounted in two armored turrets, and this is how ROLF KRAKE was armed in the German War of 1864. ROLF KRAKE's armament was subsequently twice altered and upgraded during her career, when her smoothbores were replaced with rifled cannon.

The ROLF KRAKE's most notable and historically significant design feature were the two rotating circular gun turrets to house her main 8" armament. ROLF KRAKE was also the first warship of any navy to be equipped with patented "Cole" gun turrets, named after their British designer, Captain Cowper Coles.

The modern, rotating Cole gun turrets enabled the ROLF KRAKE to train her armament on a target, independently of the direction in which ROLF KRAKE was steaming - then as revolutionary a development in warship design and armament as was the steam propulsion which emancipated warships from total reliance on the direction of the wind, in shaping the warship's course and maneuverability.

Cole gun turrets operated on the "Cole principle," i.e., the circular turrets rotated on a circular roller track located at the periphery of the base of the turret - the outer edge and weight of the turret base rested on this roller track.

In contrast to the "Cole principle" of turret rotation, the Ericsson-designed circular gun turret of the famous ironclad U.S.S. MONITOR, which fought the Confederate ironclad C.S.S. VIRGINIA at the historically significant Battle of Hampton Roads in 1863, rested and rotated on a central spindle - a design feature which seemingly placed significant, and possibly unacceptable, torsion stress on the rotating central spindle, a design feature which could possibly be criticized on this basis.

The turret of Rolf Krake
The turret of Rolf Krake

Ironically, although the two gun turrets which housed the ROLF KRAKE's 8" main armament were correctly aligned (fore and aft) on the center-line of the ROLF KRAKE's deck, this fundamental and sound design principle was gradually lost sight of in future warships designed and built in many countries, and was famously "rediscovered" in the design of the precedent-setting British battleship DREADNAUGHT of the First World War era.

Who was Rolf Krake?
Rolf Krake is a mythological Danish champion, and king, who was vaunted for his bravery and military exploits. Rolf Krake is known from an ancient saga ("fornaldarsögur"), named after him. The tale of Rolf Krake is also mentioned in the early English heroic epic poem entitled BEOWOLF.

ROLF KRAKE in Combat: The German War of 1864
Prussia and Austria, members of the "German Alliance," declared war on Denmark on February 1, 1864, over the issue of Denmark's long-standing historical relationship with the Duchies of Slesvig and Holstein, the first Duchy of which contained a sizeable Danish population. The Prussian and Austrian - i.e., "German Alliance" - armies commenced both hostilities and predatory aggression by crossing the border into Slesvig on the same day, February 1st.

As the vast majority of Denmark's warships in 1864 were wood-built, they could not be employed in close coast-defense operations in which these vulnerable warships' wooden hulls, masts and rigging would be exposed to the lethal risk of direct fire from heavy enemy shore artillery - particularly if the enemy artillery was rifled.

The Danish troopship AURORA leaving for the war
The Danish troopship AURORA leaving for the war

Therefore, since the principle and immediate military threat to Denmark was posed by the invading German armies thrusting into the Jutland peninsula, the War of 1864 was primarily a land affair between the opposing armies. Denmark, however, remained superior at sea.

In contesting the German invasion of the Jutland peninsula, the principal army operations occurred in a relatively confined area around the Danish defensive earthworks near the town of Dybbøl, just across the narrow Als Sound from the Danish town of Sønderborg. Dybbøl became subjected to a protracted, eight week German siege during which the Danish defensive positions were extensively bombarded by Prussian heavy artillery.

On February 11, 1864, ten days after Prussia and Austria invaded Slesvig, the ROLF KRAKE was placed under operational orders, under which she remained until August 11, 1864, i.e., until a month after the July 11, 1864 ceasefire which in effect ended the war. During this time, the ROLF KRAKE was under the command of the Danish naval Captain Hans Peter Rothe.

Captain Rothe's operational orders sent him and the ROLF KRAKE to Søndorborg, located on the Island of Als at the shortest of distances from both the Danish army's defensive positions at Dybbøl, and from the invading German armies who were then besieging defending Danish forces there. ROLF KRAKE was headed for combat.

ROLF KRAKE's Action at Egernsund
In its early operations around Dybbøl, the Prussian army attempted to outflank the Danish defensive positions by throwing a pontoon bridge across Egernsund, a narrow entrance to a little bay not far from Dybbøl. The ROLF KRAKE's first contact with the invading enemy armies occurred here at Egernsund, just 18 days after the German invasion, when the ROLF KRAKE closed the coast on the enemy's seaward flank with the mission of destroying the Prussian pontoon bridge.

The ROLF KRAKE in Vemmingbund
The ROLF KRAKE in Vemmingbund

Because of shoal waters near Egernsund, the ROLF KRAKE had to anchor behind a tongue of land which blocked the ROLF KRAKE's view of its target, the Prussian pontoon bridge. Therefore, ROLF KRAKE was forced to attack the bridge with indirect fire, which was not the type of fire which promised effective and rapid results against so small a target. The ROLF KRAKE proceeded to shell the pontoon bridge at a range of 1,400 yards, but failed to destroy the bridge.

In shelling the Prussian pontoon bridge with indirect fire, the anchored and stationary ROLF KRAKE was in turn taken under direct, converging fire by enemy artillery ashore, receiving over 150 hits which, however, never penetrated ROLF KRAKE's 4½" iron hull or turret armor. The Prussian artillery attack against her did, however, succeed in either disrupting or distracting the ROLF KRAKE from its attack on the Prussian pontoon bridge. ROLF KRAKE ceased fire after expending only 72 rounds, and retired from the scene after sustaining her first combat casualties - three wounded, including a turret commander.

It's not known whether the wounding of the turret commander of one of ROLF KRAKE's two turrets, thereby possibly depriving the turret crew of leadership and direction and thus perhaps incapacitating this turret - which comprised ½ of the ROLF KRAKE's main armament - played a part in the Danish captain's decision to break off the action.

In retrospect, 72 rounds seems to be an extremely low ammunition expenditure for this "surgical" type of "fire mission" by the ROLF KRAKE, particularly (1) when the fire was delivered by smoothbore cannon which lacked the long-range accuracy of rifled cannon; and (2) in circumstances where this seemingly low expenditure of ammunition occurred in a situation where the ROLF KRAKE failed to accomplish the important goal of its fire mission, e.g., raising serious questions whether a significantly greater expenditure of ammunition for this fire mission was appropiate and necessary.

The ROLF KRAKE's artillery action at Egernsund demonstrates a salient feature of sea power, that is, the strategic and tactical flexibility which sea power offers - as, in this instance, exemplified by a warship's tactical ability to outflank an enemy army's seaward flank. In this instance, in the Prussian army's attempt to outflank the Danish army's positions by its construction of a flanking pontoon bridge, the Prussians were themselves, in turn, outflanked by the ROLF KRAKE's seaborne attack on the Prussian's seaward flank - which the Prussians could not counter with their own naval forces, but only by shore based artillery.

The ROLF KRAKE's attack on the Prussian pontoon bridge at Egernsund apparently failed for two reasons: (1) the lack of effective artillery spotting system to direct ROLF KRAKE's indirect fire against the Prussian pontoon bridge, by spotting the fall of ROLF KRAKE's shot and making corrective fire adjustments; and (2) the Prussian artillery counterattack, which disrupted ROLF KRAKE's own fire mission against its designated target.

ROLF KRAKE's Actions at Dybbøl
Following its action at Egernsund, the ROLF KRAKE again provided heavy seaborne fire support to the Danish army's seaward flank ashore, in the Danish army's defense of Dybbøl, as a counter to two separate Prussian infantry attacks.

On March 28, 1864, the ROLF KRAKE shelled Prussian infantry while they were delivering an attack on the Danish army's defensive positions at Dybbøl. The ROLF KRAKE's supporting fire caught the masses of attacking Prussian infantry in the open, inflicting either heavy casualties, or a profound psychological shock detrimental to Prussian troop morale, which ultimately defeated this Prussian attack.

ROLF KRAKE in action on April 18th during the Prussian attack on Dybbøl
ROLF KRAKE in action on April 18th during the Prussian attack on Dybbøl
Ironically, in regard to the availability of the ROLF KRAKE's mobile heavy seaborne artillery support, the Prussians had chosen to locate their parallel trench approaches, toward the Danish defensive earthworks at Dybbøl, right next to the sea (i.e., their seaward flank), that is, at exactly the point where the Prussian parallels could be easily taken under heavy fire from the ROLF KRAKE.

A quick look at a map of the Prussian army positions at Dybbøl shows how exposed and vulnerable the location of these Prussian army positions were to an attack from the sea.

After eight weeks of siege, and with the Danish defensive position becoming desperate from constant Prussian bombardments and the approaching Prussian parallels, the decisive German attack on Dybbøl was delivered on April 18, 1864. Once again, the ROLF KRAKE closed the coast to provide heavy seaborne fire support to the Danish army ashore, by shelling the final German charge against Dybbøl late on April 18th. However, Dybbøl was soon lost, although the Danish army eluded destruction and managed to retreat relatively intact.

ROLF KRAKE and the German Amphibious Invasion of Als
Following the Danish loss of Dybbøl on April 18th, the only portion of the Duchy of Slesvig that remained unoccupied by the German armies was the island of Als, on which Danish army units were stationed in defensive positions.

The island Als is narrowly separated from the Jutland peninsula by Als Sound, and lies just a minuscule distance from the captured Danish earthworks at Dybbøl on the Jutland peninsula, immediately opposite from Als. In view of the close proximity of the invading German armies, the island of Als was an obvious point of a future German attack. Therefore, it was here in the vicinity of Als Sound that the Danish navy posted the ROLF KRAKE to patrol, in an attempt to dissuade or contest any attempt by the German armies to make an amphibious crossing to Als.

Unfortunately, the operational orders given to the ROLF KRAKE's commander were unclear and, furthermore, at the decisive moment, the ROLF KRAKE's captain misjudged the tactical situation and the intentions of the enemy. As a result, after initially, boldly and single-handedly engaging amphibious Prussian troop transports, in a courageous and determined effort when the Prussian army made its amphibious attempt on Als on June 29, 1864, the ROLF KRAKE abruptly - and seemingly prematurely and inexplicably - discontinued its apparently successful engagement against the Prussian boats and steamed away from Als Sound, with the ultimate result that Als was lost.

The Germans had assembled 600 boats with which to launch their amphibious assault against Als. Against these heavy odds it is highly questionable whether the ROLF KRAKE, even if she ruthlessly contested a German amphibious crossing to the extremity of risking ROLF KRAKE's own destruction in doing so, could have ultimately prevented the Germans from establishing an effective bridgehead on Als, from which the German armies could then conquer the entire island.

As a prospective matter, any attack on the Prussian amphibious invasion fleet which the ROLF KRAKE would have delivered, in the extremely narrow waters of Als Sound, would have placed ROLF KRAKE in the closest proximity to the massed Prussian shore batteries, where the muzzle velocity of the rifled Prussian cannon, and the corresponding penetrating power of their artillery projectiles, would have been the greatest and most effective against the ROLF KRAKE.

A German postcard showing the crossing to Als on June 29th.
A German postcard showing the crossing to Als on June 29th.

The ROLF KRAKE could certainly have imposed a heavy penalty in human cost on the 600-vessel German amphibious armada, by inflicting severe casualties on the embarked German troops making the amphibious attempt. However, whether such a potential cost could have been so prohibitive as to either deter or defeat a German amphibious attempt is questionable.

A quick look at a map discloses the high suitability of Als Sound in facilitating the launching and delivery of an amphibious assault, from the Jutland side, upon the opposing shoreline on the island of Als. Als Sound is relatively long, affording long shorelines on either side, from which to both launch and receive, respectively, an amphibious assault. Als Sound is also very narrow, which means that a German amphibious crossing would not involve a long and perilous passage for the German assault forces, thus exposing these forces to lengthy Danish interdiction for the duration of the passage.

The Germans had so many boats available to effect an amphibious crossing that many if not most could simply have successfully eluded the solitary ROLF KRAKE, to effect a landing on the opposite shore at Als.

The ROLF KRAKE's heavy main muzzle-loading armament had a slow rate of fire with which to engage so many small and elusive targets, and ROLF KRAKE lacked an effective, quick-firing, secondary armament with which to effectively engage small vessels. Although the ROLF KRAKE's hull was equipped with a ram, ROLF KRAKE's slow speed, and lack of maneuvering room in the confined waters of Als Sound, would probably have precluded ROLF KRAKE's [its] effective use of its ram against numerous and elusive small vessels. Therefore, without other naval support, the ROLF KRAKE probably could not have single-handedly defeated the large-scale German amphibious attempt on Als

Given the gravity of the Prussian amphibious threat against Als, was the ROLF KRAKE expendable, justifying the military expediency of sacrificing ROLF KRAKE and her crew to contest a Prussian amphibious assault?

If ROLF KRAKE had seriously contested the Prussian amphibious crossing of Als, and fought this battle to its ultimate conclusion as ROLF KRAKE would have been compelled to do in engaging so many enemy amphibious vessels, the ROLF KRAKE would probably have been lost in doing so. Emulating the fate of her namesake, the legendary Danish king Rolf Krake and his band of valiant champions, a determined and sustained attack by ROLF KRAKE on the Prussian invasion armada would probably have involved the ROLF KRAKE and her crew in heroic, self-sacrificial destruction, in nobly resisting the overwhelming odds of the enemy host.

In terms of raw, impersonal statistics, the combat loss of the ROLF KRAKE would have only involved the sacrifice of ROLF KRAKE's 140 crew members as well as the ROLF KRAKE, a costly weapons system. Conversely, by comparison, the Danish army subsequently lost 216 dead, 462 wounded, and 1,878 prisoners in the Danish army's defense of Als - a human toll on the part of the defending Danish army which the ROLF KRAKE's defensive self-sacrifice could conceivably have either prevented or mitigated.

In regard to this statistical weighing of potential alternative human costs of defending Danish soldiers or sailors, could the ROLF KRAKE's sustained and self-sacrificial attack on the Prussian invasion armada have bought sufficient critical time to enable the Danish foot soldiers on Als to effectively deploy to meet and successfully contest the Prussian attack? Probably not. The Danish army's (i.e., infantry's) position on Als was basically untenable.

The German capture of Als was not a decisive event in any case. The Germans did not need to capture Als in order to successfully conclude the war in their favor - at the juncture immediately before the Germans launched their amphibious attack on Als, the Prussians and Austrians had already in effect won the war.

Shortly after the German armies' occupation of Als, i.e., on July 11, 1864, a ceasefire was arranged between the combatants, which in effect finally ended the war.

ROLF KRAKE and Heavy Naval Gunfire Support
During her combat operations in the German War of 1864, the ROLF KRAKE never engaged an enemy warship, although at the Danish island of Als the ROLF KRAKE did in fact, albeit briefly, engage elements of the armada of 600 vessels the Prussians had assembled to effect their amphibious crossing to attack the island of Als.

Although the ROLF KRAKE never engaged enemy warships, the unique combat role the ROLF KRAKE did perform during the German War of 1864 was in providing mobile, heavy seaborne gunfire support to the Danish army's land operations - the emphasis here is on "heavy" gunfire.

The ROLF KRAKE's main armament consisted of 8," or 68 pounder, cannon. From the perspective of heavy seaborne gunfire support, these heavy, 68 pounder cannon were substantially heavier than either the 12 pdr. cannon which was the main field piece of Napoleon's armies a half a century prior to ROLF KRAKE's time, or the new, very lightweight, small caliber, rifled 4 pdr. cannon which had just been introduced into the Danish army prior to the German War of 1864.

With its heavy 68 pounder weapons, the ROLF KRAKE could and did provide mobile, seaborne, heavy artillery bombardment support with cannon of a size that field armies - whose field artillery was horse-drawn - would be utterly incapable of employing in mobile operations in the field, but only in stationary siege operations.

ROLF KRAKE's heavy naval artillery could have a major demoralizing, if not physically destructive, effect on enemy troops, while simultaneously enhancing the moral of Danish troops. Thus, the ROLF KRAKE's mobile, heavy, seaborne gunfire support not only provided the Danes with a significant unilateral tactical advantage wherever ROLF KRAKE employed such heavy gunfire support, but the ROLF KRAKE's engagement in this unique heavy fire support role also marked a significant instructive precedent for naval warfare in the modern era - a lesson whose value would increase with the evolving potency and destructiveness of heavy naval artillery.

The ROLF KRAKE's shallow draft - of a maximum 10' 6" - was ideal for closing a coast (particularly a coast with shoal waters) on an enemy's seaward flank, to extend the reach of ROLF KRAKE's naval artillery range against enemy army forces operating inland. Because the smoothbore cannon with which ROLF KRAKE was armed in 1864 lacked great range - i.e., the range of rifled cannon - ROLF KRAKE would be compelled to deploy close inshore, to close the artillery range so ROLF KRAKE's smoothbores could effectively deliver its offshore gunfire against enemy army units on the enemy's seaward flank.

The low freeboard of the ROLF KRAKE's hull offered a relatively small target to enemy shore gunners, and ROLF KRAKE's seaborne mobility could make her a moving and, therefore, difficult target for stationary enemy shore batteries, which would have to continuously adjust their fire in order to to track their moving target - i.e., in the absence of blanket, area fire by massed shore artillery.

Plan of the ROLF KRAKE
Plan of the ROLF KRAKE

In the event enemy shore gunners could secure heavy caliber artillery hits on ROLF KRAKE, her hull and turret sides were protected by her thick iron armor, as was evident the first time German artillery units took the ROLF KRAKE under fire, off Egernsund on February 18, 1864.

In assessing the degree of effectiveness of the ROLF KRAKE's heavy seaborne gunfire support to assist the Danish army's ground operations ashore in 1864, one critical open question is what type of ammunition did the ROLF KRAKE actually employ in this role in 1864 - e.g., was it solid shot, explosive shell (with either anti-personnel fragmentation or concussion effect), or grape shot?

Although by 1864 explosive shells had been widely available to European armies for some time, and were also by far the most effective type of ammunition to utilize in gunfire support missions against enemy ground troops operating in the open, naval ships at this time typically employed solid shot as being the most effective which to penetrate the hulls of enemy warships (i.e., their most likely targets), in preference to explosive shells, which were highly effective against wooden-hulled warships but which were useless against armored warships. Thus, solid shot as opposed to explosive shell would have been the most likely type of projectiles to be available in a warship's magazines in 1864, if their likely opponents were armored warships.

It is [therefore] presumed that in 1864, the ROLF KRAKE's magazine was equipped with solid shot rather than explosive shells with which to discharge her fire support missions - unless the manufacturer of the ROLF KRAKE's 68 pdr. cannon had provided the Danish navy with a variety of types of ammunition with which to employ in ROLF KRAKE's naval cannon. In this regard, in her capacity as an armored warship, the role ROLF KRAKE was presumably designed to perform was as a counter to enemy armored warships, and not to engage in anti-personnel actions against enemy ground troops.

Solid shot would have considerably diminished the potential destructive, demoralizing and anti-personnel effect of ROLF KRAKE's shore bombardments in 1864. However, it is not in fact known what type of ammunition ROLF KRAKE actually employed when providing fire support ashore in 1864 and, therefore, the possible extent of the destructive and demoralizing effect of the ROLF KRAKE's shore bombardments.

Regarding possible ammunition types available to ROLF KRAKE, the ROLF KRAKE is reported to have employed grape shot, or possibly canister, as well as explosive shells, in its anti-amphibious action against Prussian boats in Als Sound, where the shorter gun-ranges involved in the confined waters of Als Sound would have uniquely, and fortuitously, enabled the ROLF KRAKE to effectively employ short-ranged, anti-personnel ammunition, e.g., grape shot.

The Danish Navy's 1849 Disaster in Heavy Seaborne Gunfire Support
The ROLF KRAKE's role in providing mobile, heavy seaborne gunfire support in 1864 to the Danish army's operations ashore should be seen in historical perspective.

Prior to 1864, the Danish navy had attempted to utilize Danish warships to provide mobile, heavy seaborne gunfire to attack entrenched enemy positions ashore, with utterly disastrous results to the Danish naval warships involved.

Just a mere fifteen years prior to the "armored battery" ship ROLF KRAKE's 1864 debut in providing mobile, heavy seaborne gunfire to support Danish army units, the Danish navy had ill-advisedly sent the extremely vulnerable, wooden, 84-gun Danish fleet flagship CHRISTIAN VIII, together with the equally vulnerable, wooden, 48-gun frigate GEFION - both powered exclusively by sail - as well as the Danish navy paddle-wheelers HEKLA and GEJSER, to attack entrenched rebel German coastal batteries at Eckernförde. The date was April 4, 1849.

Battle by Eckernförde
Battle by Eckernförde

The result of the Eckernförde action was highly predictable. Under the enemy's close range artillery fire, which employed ship-destroying red-hot shot (as the Danish navy should have anticipated from a coastal battery), the Danish fleet flagship CHRISTIAN VIII caught fire and blew up, and the GEFION grounded was captured intact by the Germans.

The two Danish paddle-wheelers were unable to tow these heavy Danish wooden warships out of German artillery range before the disaster occurred.

When in 1864 the ROLF KRAKE was similarly engaged in providing heavy seaborne artillery support against shore targets, comprised of an even more modern and better armed Prussian enemy, the ROLF KRAKE's unique attributes of iron armor protection and steam propulsion prevented a repeat of the 1849 Danish naval disaster at Eckernforde.

Unsuitability of Denmark's "Broadside Ironclads" to Provide Heavy Seaborne Gunfire Support Close Inshore
Regarding ROLF KRAKE's suitability to deliver heavy seaborne gunfire support during the German War of 1864, Denmark's "broadside ironclads" were the only other Danish warships of the period that might have been suitable for this type of operational employment, because they were the only other Danish warships beside the ROLF KRAKE that had armor protection to shield them from counter-battery fire from enemy shore artillery.

What disqualified Denmark's broadside ironclads from employment in the heavy gunfire support role was their deep drafts, which prevented them from approaching close inshore in Denmark's shoal territorial waters - particularly as Denmark's broadside ironclads were armed, at the time, with range-limiting smoothbore cannon.

Of Denmark's three broadside ironclads, only the DANNEBROG had completed in time to take part in the German war of 1864. However, DANNEBROG's maximum draft - which was located aft, as in most ships - was 22' 6½". Therefore, DANNEBROG's maximum draft was nearly twice the ROLF KRAKE's maximum draft of 10' 6" - which seriously restricted the geographical areas of Denmark's shoal territorial waters where DANNEBROG could be employed for coastal defense operations.

The Ironclad DANNEBROG
The Ironclad DANNEBROG

The deep drafts of Denmark's two remaining broadside ironclads were also disqualified from seaborne artillery support operations close inshore. Furthermore, the Danish broadside ironclad PEDER SKRAM was not launched until October, 1864, and the broadside ironclad DANMARK did not even arrive in Denmark from its Scottish builders until October, 1864.

Therefore, both of these Danish broadside ironclads did not become available to the Danish navy until several months after the conclusion of the German war of 1864. However, even if these ships had been available to the Danish navy in time to participate in operations during the 1864 conflict, their maximum drafts, of 21' and 18' 6" respectively, would have seriously limited their usefulness in providing heavy gunfire support close inshore.

The First Combat Between Two Armored Ships: Comparative Evaluation with ROLF KRAKE
On August 28, 1862, when the Danish Admiral Steen Bille signed the contract for the construction of the ROLF KRAKE, the first combat in world history between two armored warships had already taken place just six months earlier, on March 9, 1862, during the Civil War in the United States.

This first combat between two armored ships occurred in the Battle of Hampton Roads, when the Confederate ironclad C.S.S. VIRGINIA attempted to break the Union blockade of the South by seeking to destroy Union fleet's wooden blockading warships.

However, VIRGINIA was engaged by the Union ironclad U.S.S. MONITOR. After blasting away at each other for four hours, neither ironclad could seriously damage the other.

The Ironclad U.S.S. MONITOR rams the VIRGINIA.
The Ironclad U.S.S. MONITOR rams the VIRGINIA.

The MONITOR's turret mounted two 11" muzzle-loading smoothbores, whereas the ROLF KRAKE's two armored turrets each mounted a roughly comparable two 8", 68 pdr., muzzle-loading smoothbore cannon. Conversely, 4 of the VIRGINIA's 10 heavy cannon were rifled, i.e., two 7" Brooke "rifles" and two 6.4" Brooke "rifles."

The U.S.S. MONITOR, like the ROLF KRAKE, had a rotating armored turret which housed its main armament. One combat advantage the MONITOR's crew noted in having a rotating turret was that after firing their 11" muzzle-loaders, the MONITOR's turrets could be rotated away from enemy fire so that the MONITOR's muzzle-loading cannon could be loaded without exposure to enemy fire - the same would have applied to the ROLF KRAKE.

To provide perspective on the relative contemporary strength of the ROLF KRAKE's own iron armor protection, the iron armor mounted on the side of the MONITOR's hull was 4½" thick, or nearly the same as the ROLF KRAKE's, which ranged between 4½" to 3" in thickness. The MONITOR's deck iron was only 1" thick.

While the MONITOR's iron turret armor in the immediate vicinity of the turret's gunports was 9" thick, the ROLF KRAKE's iron turret armor around its turret's gunports was a comparable 7" thick. However, whereas the balance of the MONITOR's turret armor was 8" thick, that of ROLF KRAKE was only 4½" thick - which meant that if, like the MONITOR, the ROLF KRAKE rotated her gun turrets away from the enemy in order to reload her smoothbores, the thinner armor of the rear of ROLF KRAKE's turrets would have been exposed to enemy fire.

Regarding the strength of turret armor, the MONITOR'S freeboard was so low that during the Battle of Hampton Roads in 1863 it was almost exclusively the MONITOR's armored iron turret which received the fire from the VIRGINIA's heavy guns - often at point-blank range, where the VIRGINIA's rifled cannons' muzzle velocity and, hence, the cannon projectiles' iron armor penetrating power, would have been the greatest.

Similarly, in its action at Egernsund, ROLF KRAKE's turrets seemed to have borne the brunt of the Prussian artillery fire.

The turret of the MONITOR
The turret of the MONITOR

If the MONITOR's 8" to 9" thick iron turret armor could not be penetrated at point-blank range by the VIRGINIA's powerful rifled cannon, it is unlikely that ROLF KRAKE's 7" iron turret armor could have been penetrated by similarly powerful cannon, but firing at much longer ranges (e.g., from heavy enemy shore artillery) at which the kinetic energy, and corresponding penetrating power, of the cannons' projectiles would have become progressively diminished.

One particularly novel design feature employed in the ROLF KRAKE's turrets, that was not present in MONITOR's turret design, is that the ROLF KRAKE's turrets were recessed as far as possible into the ROLF KRAKE's hull, thereby proportionately reducing the amount of the ROLF KRAKE's turrets which were exposed to enemy fire - an ingenious solution to the protection of ROLF KRAKE's turrets.

One criticism leveled at the ROLF KRAKE's design is that, unlike the clear arc of fire offered by the MONITOR's unencumbered deck, the arcs of fire of ROLF KRAKE's turrets were obstructed by the ROLF KRAKE's masts and other deck fixtures, so that ROLF KRAKE's heavy guns could fire neither directly forward nor directly aft.

However, this criticism is less persuasive than first appears. Battery-armed warships historically have steered at an angle where both their turrets could be simultaneously brought to bear on a target, to increase the probably of obtaining a hit. The ROLF KRAKE would have presumably done the same, i.e., not fired her guns either directly ahead or astern.

ROLF KRAKE's Uncanny Similarities to U.S.S. MONITOR
The ROLF KRAKE, ordered just six months after the MONITOR's historic action at Hampton Roads, bears some uncanny similarities to the MONITOR. Most visually notable is the striking resemblance of the contour of the MONITOR's deck compared to that of the ROLF KRAKE.

It would be instructive to compare the cross section of the MONITOR's hull at the location of the MONITOR's turret, with a similar cross section of the ROLF KRAKE's hull.

Also striking are the similarities of the MONITOR's and the ROLF KRAKE's hull dimensions. The MONITOR was 172' long overall, 41' 3" maximum beam, and 10' 6" draft, compared to the ROLF KRAKE's 183' length, 38' 2" beam, and 10' 6" draft. Thus, the two ship's drafts were identical, while ROLF KRAKE had a narrower beam but longer hull.

On their largely similar dimensions, ROLF KRAKE was able to mount two gun turrets to the MONITOR's one. ROLF KRAKE's ability to do so becomes evident in a comparison of the side profiles of the two ships, which are glaringly different from one another. ROLF KRAKE had a greater hull volume underwater than did the MONITOR, giving ROLF KRAKE the stability to ship two gun turrets instead of one. The lower underwater volume of the MONITOR's hull on essentially similar hull dimensions is indicated by the fact that the MONITOR only displaced 987 tons to the ROLF KRAKE's 1,320.

Was ROLF KRAKE Completely Immune?
The most vulnerable part of the ROLF KRAKE's hull was her open upper weather-deck, which was not armored. Therefore, the most lethal potential danger to the ROLF KRAKE was from "plunging" heavy Prussian artillery fire, descending at an arc from heavy shore artillery firing at steep, high angle trajectories onto the ROLF KRAKE's vulnerable, unarmored open deck.

Regarding the armored areas of the ROLF KRAKE's hull, in contrast to her unarmored deck, it's not known if the ROLF KRAKE was completely immune or impervious to any form of artillery fire the Germans could have employed against her. In this regard, the performance characteristics of the types of artillery pieces the Germans employed, or could have employed, against the ROLF KRAKE in 1864 are not known.

The types, properties and ballistic performance, and anti-armor effectiveness, of the projectiles the German artillery could have employed against the ROLF KRAKE are also not known.

The types of projectiles employed in the MONITOR - VIRGINIA combat were solid shot, at least by the MONITOR, and the VIRGINIA presumably also employed solid shot. As demonstrated in the MONITOR vs. VIRGINIA combat, the penetrative power of solid shot against each ironclad's armor was virtually nil - and the thickness of ROLF KRAKE's armor plate was comparable to that of the MONITOR and VIRGINIA. Similarly, field artillery's use of explosive shell against armor plate would have been equally ineffective, as lacking in sufficient penetrative power against thick armor plate.

Facts - Lieutenant Jespersen

The only Danish naval officer to be killed during the war of 1864, was Lieutenant Jespersen who was killed onboard the ROLF KRAKE, during the Prussian assault on the Danish positions at Dybbøl. This stone was put up for him at Dybbøl.

If the types of artillery ammunition available to the Germans in 1864, and which could have employed against the ROLF KRAKE, included forms of more destructive explosive shells, with greater penetrative power sufficient to pierce available armor plate, then perhaps the ROLF KRAKE's side armor would have been potentially vulnerable to enemy field artillery under certain circumstances..

To reiterate, ROLF KRAKE's greatest vulnerability was to steep trajectory, "plunging" fire, and this vulnerability was not simply theoretical. On April 18, 1864, while ROLF KRAKE was providing defensive gunfire support during the last German attack against the Danish army positions at Dybbøl, a plunging German shell penetrated the ROLF KRAKE's unarmored deck, and exploded below deck, causing casualties and serious damage to the interior of the ship.

Following the conclusion of the German War of 1864, the ROLF KRAKE engaged in further experimental trial cruises in 1866 and 1867, and then participated in squadron exercises with the Danish fleet throughout the 1870s, together with other new, modern warships of the Danish navy which had succeeded the trend-setting ROLF KRAKE in entering Danish naval service, such as the low freeboard, Danish-built, iron "turret ships" GORM and LINDORMEN.

The ROLF KRAKE continued to be actively employed throughout the 1880s, and in early 1890s, at the end of her active service life, was utilized as a test ship.

ROLF KRAKE was stricken from the Danish Navy list on June 29, 1907, after an unusually long career of over forty years of service. ROLF KRAKE's hull was stripped, sold for scrapping, and was towed to Dordrecht in the Netherlands, where her scrapping took place in 1907.

The Danish Navy's Coast Defense Role
ROLF KRAKE's delivery of heavy seaborne gunfire support against an invading enemy army's seaward flank, in support of the Danish army defensive operations ashore, and the ROLF KRAKE's anti-amphibious patrol work off the island of Als during the War of 1864, highlights the centrality of the Danish navy's historic coast defense role, and illustrates the innovative part ROLF KRAKE played in performing these two coast defense roles at the dawn of the modern warship era.

Hans Peter Ludvigsen, sailor onboard the ROLF KRAKE ca. 1880. (Photo from Jesper Stenild)
Hans Peter Ludvigsen, sailor onboard the ROLF KRAKE ca. 1880. (Photo from Jesper Stenild)

The Danish navy's historic coast defense role acquired new significance following Denmark's abrupt loss of her "big power" fleet status in 1807 and, with the loss of
Denmark's ocean-going fleet, the Danish navy's ability to provide Danish national territory with "distant" coast defense protection, in the form of deep water fleet operations aimed at foiling, inter alia, enemy amphibious assaults on Danish national territory. But what about Denmark's Jutland peninsula which, while possessing an extensive, exposed coastline with associated shoal waters, was primarily vulnerable not to amphibious but to enemy land attack?

ROLF KRAKE, an entirely new form of coast defense warship, demonstrated an entirely new form of "close" support in providing coast defense, i.e., close support in the form of heavy, mobile, seaborne gunfire support, on the Danish army's seaward flank, to the assist the defensive operations of the Danish army ashore - against an enemy army invading Denmark's Jutland peninsula.

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Further reading
B. Degenkolv, Den Danske Flaades Skibe i Sidste Aarhunderede (1906)
R. Steen Steensen, Vore Panserskibe 1863-1943 (1968)
R. Steen Steensen, Vore Krydsere (1971)
Johs. Nielsen, The Danish-German War 1864 (1991)
Johs. Nielsen, The Schleswig-Holstein Revolt 1848-1850 (1993)
Ole Lisberg Jensen, The Royal Danish Navy: An Introduction to the History of the Royal Danish Navy (1994)
Palle Lauring, A History of Denmark (1960)
Robert Gardiner (editorial director), Conway's All the World's Fighting Ships 1860-1905 (1979)
Arnold A. Putnam, "ROLF KRAKE, Europe's First Turreted Ironclad," in the MARINER's MIRROR, Vol. 84, No. 1 (February, 1998), pp. 56-63.
Stuart Penhall, "The Capture of the Island of Als," Danish Military History website.

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