After Prussia and Austria had already largely brought the duchies of Schleswig and Holstein under their control as a result of the Prussian Battle of Dybbøl, an armistice came into force on May 12, 1864.

After the failure of peace negotiations at the London Conference of 1864, Prussia and Austria agreed in their June 1864 Carlsbad Agreement to resume the war.

With the end of the truce, the conquest of the remaining parts of the duchies began, including the Wadden Sea Islands on the west coast of Schleswig.

However, Amrum, southern Rømø, northern Sylt and western Föhr did not belong to the Duchy of Schleswig, but were part of Denmark.

The west coast of Schleswig-Holstein fell into Austria's area of operations and Rear Admiral Bernhard von Wüllerstorf-Urbair decided to conquer the islands.

Due to bad weather, the Austro-Prussian flotilla left Cuxhaven for the theater of operations two days later than planned on July 11.

When they came under fire again, they simply pulled the small rowboats onto a sandbank and waited for the tide to go out, which forced the gunboats to retreat.

At 6 a.m. on July 18, the Danish flotilla began being shelled in the port of Wyk auf Föhr and the occupation of Langeness and Gröde.

As a result, on July 19, seven officers, two civil servants and 185 men from the Danish flotilla surrendered to the Allied forces in view of the hopeless situation.

He was only caught in the evening by the Prussian gunboat Blitz, then lowered the flag and handed over his sword with his first officer at 7:30 p.m., a few hours before the armistice came into force.

Due to the outcome of the war and the resulting Peace of Vienna, the islands initially became part of the Austrian-Prussian Condominium in Schleswig-Holstein.