Battle of Dybbøl The Battle of Dybbøl ( ; ) was the key battle of the Second Schleswig War and occurred on the morning of 18 April 1864 following a siege starting on 7 April . Denmark suffered a severe defeat against Prussia , which decided the war . Dybbøl was also a battlefield in the First Schleswig War . Background . Following the annexation of the Duchy of Schleswig in November 1863 by the Danish king Christian IX ( who was also the Duke of Schleswig ) , Prussian and Austrian troops invaded Jutland in January 1864 . The defending Danish army were equipped with smaller guns and an older type of rifle . The Prussian army used the Dreyse needle - gun , a breech - loading rifle that could be loaded while the user was lying down . Since the Danes had to load their older muzzle - loading rifles while standing , they were better targets for the Prussians . The Dybbøl fort lies in a short blunt peninsula that defends against access to the fort by land and featured an enclosed pier for the ferry across the Alssund to Sønderborg on the island of Als . The Dybbøl position was ill - prepared due to too much effort spent fortifying the Dannevirke . Dybbøl particularly lacked safe shelters in the forward line , but worse , the technological developments in artillery ( particularly long - range rifled guns ) had made the geography of the position unsuited for a lengthy defense . The line had too little depth , and across the waters of the southern inlet ( forming the southern part of the peninsula ) modern guns could subject the main defensive line to raking fire along the length of the line . This meant that not only was the position effectively saturated during the approximately two months of bombardment , but also most of the defending crew had to be withdrawn far behind the line because of attrition by the bombardment and lack of effective shelters , and when the storm assault was finally initiated , the line was consequently undermanned by tired and demoralised troops . The Danes did have one major advantage in that they had more or less unchallenged command of the sea and so were able to deploy the modern ironclad " Rolf Krake " to the scene to support Danish ground forces at Dybbøl with shore bombardments from its turret mounted 8 inch guns . For much of the siege of " Rolf Krake " was used as a mobile heavy seaborne artillery platform and the Prussians were almost helpless to counter it since they had no naval forces of their own capable of matching the Danish navy , a fact that sapped Prussian morale . The firepower of the " Rolf Krake " was not exploited as well as it could have been . It has been pointed out that the vessel could have been employed to more aggressively shell the Prussian siege works which were relatively exposed to naval bombardment but the ship nevertheless rendered invaluable support . Battle . On the morning of 18 April 1864 at Dybbøl , the Prussia ns moved into their positions at 02 : 00 am . At 10 a . m . the Prussian artillery bombardment stopped and the Prussians charged through shelling from the " Rolf Krake " which did not prove enough to halt them . Thirteen minutes after the charge , the Prussian infantry had already seized control of the first line of defence of the redoubt s . A total massacre of the retreating troops was avoided and the Prussian advance halted by a counterattack by the 8th Brigade , until a Prussian attack threw them back ; that attack advanced about 1 km and reached Dybbøl Mill . In that counterattack the 8th Brigade lost about half their men , dead or wounded or captured . This let the remnants of 1st and 3rd Brigades escape to the pier opposite Sønderborg . At 13 : 30 the last resistance collapsed at the bridgehead in front of Sønderborg . After that there was an artillery duel across the Alssund . During the battle around 3 , 600 Danes and 1 , 200 Prussians were either killed , wounded or disappeared . A Danish official army casualty list at the time said : 671 dead ; 987 wounded , of which 473 were captured ; 3 , 131 unwounded captured and / or deserters ; total casualties 4 , 789 . The 2nd and 22nd Regiments lost the most . Also , the crew of the Danish naval ship " Rolf Krake " suffered 1 dead , 10 wounded . The Battle of Dybbøl was the first battle monitored by delegates of the Red Cross : Louis Appia and Charles van de Velde . Following the battle , the Prussians used the fort area as a starting point to attack Als in June 1864 . Aftermath . While the battle of Dybbøl was a defeat for the Danes the activities of the " Rolf Krake " along with other Danish naval actions during the conflict served to highlight the naval weakess of Prussia . In an attempt to remedy this the Austro - Prussians dispatched a naval squadron to the Baltic which was intercepted and soundly defeated by the Danish Navy at the Battle of Helgoland . A peace treaty was signed on October 30 , 1864 that essentially turned the duchies of Schleswig and Holstein into an " Austro - Prussian condominium , under the joint sovereignty of the two states . " The German chancellor , Otto von Bismarck , had taken one of the first steps toward launching the German Empire that would dominate Europe until World War I . Legacy . Every year on 18 April a national memorial is held in Dybbøl . Danish soldiers appear in period uniforms . The 140 year anniversary ( in 2004 ) was a special event in Denmark . Sociologists still refer to the Battle of Dybbøl when commenting on the relationship between Danes and Germans . Karl Klinke , a Prussian soldier who is said to have run onto the redoubt carrying explosives and igniting them by the palisades thus killing himself and blowing a hole into the Danish redoubt , was immortalized in a poem written by Theodor Fontane . Johann Gottfried Piefke , a composer of well - known military marches , dedicated the " Düppeler Schanzen Sturmmarsch " to this battle . ( See [ in German ] . ) On the field of Dybbøl were formerly national symbols of both warring sides : the Danish Dybbøl Mill and the German Düppeldenkmal . Dybbøl Mill still stands , but the German victory monument was blown up in 1945 . The perpetrators were never identified , and this monument has never been rebuilt .