sentences:  However the "Bismarck" operation had disrupted U-boat operations and only two ships sunk in latter two weeks of May; one of these was "Empire Storm", sunk by "U-557" on 29 May.On 1 June "U-557" re-fuelled from supply ship "Belchen", but later that same day "Belchen" was caught and sunk by Royal Navy units engaged in hunting down the Operation Rheinübung supply train.On 3 June "U-557" joined Group "West", but the group had no success; this period following the capture of "U-110" and the consequent penetration of German Enigma code meant the Allies were able to re-route threatened convoys around areas of known U-boat activity and losses were kept to a minimum.