Unterseeboot 20

During World War I, U-20 was launched on December 18, 1912, and commissioned into the Kaiserliche Marine on August 5, 1913.

On May 7, 1915, U-20 was patrolling off the southern coast of Ireland under the command of Kapitänleutnant Walther Schwieger. Three months earlier, on February 4, the Germans had established a submarine blockade around the UK and had declared any vessel in it a legitimate target.

At about 1:40pm Schwieger saw through his periscope a vessel approaching. From a distance of about 700 meters Schwieger noted four funnels and two masts, recognized RMS Lusitania, an element of the British Fleet Reserve, and fired a single torpedo. The torpedo struck on the starboard side, almost directly below the bridge. After the explosion of the torpedo, the liner was shattered by a
second explosion (possibly caused by coal dust, possibly caused by war munitions in Lusitania's hold) so huge that Schwieger himself was surprised. Lusitania sank rapidly with the loss of nearly 1,200 lives, among them 128 Americans. The exact amount of time it took Lusitania to sink is not consistently reported, but was not more than 25 minutes.

Fifteen minutes after he had fired his torpedo, Kptlt. Schwieger noted in his war diary:"It looks as if the ship will stay afloat only for a very short time. [I gave order to] dive to 25 metres and leave the area seawards. I couldn't have fired another torpedo into this mass of humans desperately trying to save themselves."

There was and is great controversy about the sinking, not only as to whether the rules of engagement permitted Schwieger to attack and whether Lusitania was smuggling contraband war material to England, but also over minutiae such as the number of torpedoes Schwieger fired. For a discussion of these issues, see RMS Lusitania.

The second U-20 was a Type IIB submarine of the Kriegsmarine. Her keel was laid down August 1, 1935 by Germaniawerft, of Kiel. She was commissioned February 1, 1936.

She had numerous commanding officers over her eight-year career: