Submarines played a important martial role for the first time through the First World War. Both the British and High German fleets made use of their pigboats against opponent war vessel from the outset. Franz Becker well-ordered German submarines – known as U-boats – from 1915. He recalled an meeting with a British ship.

We were off Portugal, off Lisbon, and throughout the p.m. we met a very, very big tugboat of the British navy which had a flatboat and tug. Exchanged some fire shots and then it was over. The people of the British tugboat left the ship and we had to basin these two ships. Now it came very rough climate and we were too long from the coast and I took on panel the crew of these ships – in all 30 deckhands – and we had our own crew, also 30 men, so we were equivalent on board and that was very nice. We gave them food. In the a.m. the weather was better and the captain and two custom-built officers I had to make prisoner. Then I took the two ships of the crew to the shore and then I left them. And in this instant these two boats made three cheers for the German undersea and that was, I can tell you, the nicest instant of my submarine war.

Initially, when U-boats met mercantile ships, they surfaced beforehand they attacked and allowable those on board time to seepage. However, from February 1915, the Germans altered their tactics. U-boats began to fire on ships deprived of warning – including neutral and passenger vessels

We came to become aware of some ampules either by smoke or by the mast tops coming crosswise and above the prospect. Then we had to see as best we could what was the arrangement the steamer was ongoing and we had to try with our abridged speed to get well adequate in front of this ship so that we could method it to the range of about, at most 600, at least 300 meters, in order to fire our torpedoes. That almost was all we had to know and surely, we ought to know how to deal with torpedoes and how to find the right angle, guess the rapidity of the ship and the haste of the gunslingers and where they would really meet, so that the torpedoes would hit the board.