 Constructed by Kaiserliche Werft Danzig, "U-15" was ordered on 23 February 1909 and was commissioned three years later on 7 July 1912.The boat left port for its first patrol on 1 August 1914, but on 9 August, "U-15" was forced to lie stopped on the surface off the coast of Fair Isle, in Shetland, Scotland, after its engines had failed.While stranded on the surface, the British warship spotted the boat through a thick fog and could hear hammering from inside the boat as the crew tried to repair the damaged engines.