the Austrians and Prussians to break the Danish blockade of the North Sea coastal ports at the Battle of Heligoland on 9 May. The Austrians, fearing that a more aggressive operation to defeat the Danish fleet in the Baltic would provoke the British, kept their squadron in the North Sea for the remainder of the war. On 9 May, the two sides signed an armistice in London that took effect three days later, temporarily ending the fighting. The armistice lasted until 26 June, when fighting broke out again on land. The Austrian and Prussian naval forces in the North Sea supported operations to capture the islands off the western Danish coast. These advances, coupled with the capture of the island of Als in the Baltic Sea, forced the Danes to seek a second armistice on 29 June. Ultimately, Denmark sued for peace after it became clear that they had lost naval superiority and that Britain would not intervene in the conflict. Order of battle Denmark Squadron commander: Rear Admiral Carl Edvard van Dockum Prussia Squadron commander (Commodore): Captain Eduard von Jachmann Footnotes References Further reading Conflicts in 1864 Naval battles and operations in the Baltic Sea Naval battles involving Denmark Naval battles involving Prussia Naval battles of the Second Schleswig War Rügen Battle of Jasmund 1864 in Prussia 1864 in Germany March 1864 events