First world war: how total submarine warfare was declared 100 years ago

Striking images of adventurous day-trippers scrambling on board wrecked first world war German submarines off the coast of Cornwall have been released to mark the centenary of the day life at sea became infinitely more perilous for British mariners.

On February 1, 1917, Germany declared unrestricted submarine warfare, meaning that its U-boats would torpedo any British ships or those trading with the UK without warning.

UK heritage group Historic England is also upgrading national memorial to submariners on the Thames embankment at Temple Pier in London.

The sculpture by Frederick Hitch, showing a cross-section of a submarine surrounded by allegorical figures, was unveiled in 1922 in memory of the third of the submarine service’s total personnel who died in the war, the highest percentage of any of the armed forces. Submarines had been moored near the pier as early as 1907 and in August 1916 a captured German U-boat was moored there as a tourist attraction.

Roger Bowdler, director of listing at Historic England, said: “The declaration of unrestricted submarine warfare in February 1917 was a decisive moment in the first world war. Germany’s tactic led to devastating losses for many nations, but it also horrified the world. It was seen as uncivilised, ungentlemanly, and ultimately brought the might of the United States into the war.”