During the Second Schleswig War, Tegetthoff as a "Kommodore" was given command, in February 1864, of a small Austrian squadron that sailed to the North Sea to support the very weak Prussian naval forces against the superior Danish navy which was blockading northern German ports. He was engaged by a Danish squadron commanded by Edouard Suenson at the Battle of Heligoland, in which Tegetthoff's flagship, the screw frigate "Schwarzenberg", caught fire in a close-range gunnery fight with the Danish frigates "Niels Juel" and "Jylland". Although the action was a tactical defeat for Tegetthoff, he achieved his main objective since the Danish squadron was shortly thereafter recalled to Copenhagen, lifting the blockade of the Elbe and Weser ports. Tegetthoff's telegraphic dispatch was answered by Emperor Franz Josef I with another on 12 May 1864 promoting him "Kontreadmiral" (Rear Admiral) and conferring upon him the Order of the Iron Crown.