Edited sentence: By the end of June 1915, the Germans had assembled a further 3 prefabricated Type UB I submarines at Pola, 2 of which were to be transferred to the Austrian Navy.The German Navy sent their first submarines to the Mediterranean in response to the Anglo-French Dardanelles campaign, after it became obvious that their Austro-Hungarian allies could do little against it with their small submarine force, which nevertheless was successful in defending the Adriatic.The first U-boats sent, U-21 and the two small coastal boats, UB-7 and UB-8, achieved initial success, U-21 sinking the Royal Navy predreadnought battleships HMS Triumph and HMS Majestic on 25 and 27 May respectively on her way to Constantinople, but ran into severe limitations in the Dardanelles, where swarms of small craft and extensive anti-submarine netting and booms restricted their movements.They were also assembling 3 Type UC I minelaying submarines, which were ordered converted into transports to carry small quantities of critical supplies to Turkey