SM U-20 was a German Type U 19 U-boat built for service in the Kaiserliche Marine. She was launched on 18 December 1912, and commissioned on 5 August 1913. During World War I, she took part in operations around the British Isles. The U20 became infamous following her sinking of the British ocean liner RMS Lusitania on 7 May 1915, an act that dramatically reshaped the course of World War I.
On 7 May 1915, U-20
was patrolling off the southern coast of Ireland
under the command of Kapitänleutnant Walther Schwieger
. Three months earlier, on 4 February, the Germans had established a U-boat blockade
around the United Kingdom
and had declared any vessel in it a legitimate target.
At about 1:40 pm Schwieger saw a vessel approaching through his periscope. From a distance of about 700 m
Schwieger noted she had four funnels and two masts making her a liner of some sort. He recognised her as the Lusitania
, a vessel in the British Fleet Reserve, and fired a single torpedo. It hit on the starboard side, almost directly below the bridge. Following the torpedo's explosion, the liner was shattered by a second explosion, possibly caused by coal dust, munitions in the hold, or a boiler explosion, so large Schwieger himself was surprised. Lusitania
sank rapidly in 18 minutes with the loss of nearly 1,200 lives.
Fifteen minutes after he had fired his torpedo, Schwieger noted in his war diary
- "It looks as if the ship will stay afloat only for a very short time. dive to 25 metres......