 Nyorai kuenderera mberi kweiyi ndima - Pakutanga kweHondo Yenyika II, akaiswa mungarava yehondo, achitora chikamu muHondo yeWesterplatteuye Hondo yeHel. Akachinjirwa kuU-boat Arm muna 1940, pakutanga achishanda semukuru wevarindi pa U-68 kutanga kwa1941. Achitungamirira U-68 pamabasa mashanu ehondo, achifamba muAtlantic Ocean, Gungwa reCaribbean neIndian Ocean, akapiwa Knights Cross yeIron Cross musi wa13 Chikumi 1942 uye Oak Leaves kune Knights Cross yake musi wa16 Mbudzi 1942. Parwendo rwechipiri, Merten akabatsira kununura vashandi vechikepe chinobatsira Atlantis uye chikepe chinotakura mafuta Python, chakanga chanyudzwa neRoyal Navy. MunaJanuary 1943 Merten akava mutungamiri we26th U-boat Flotilla uye muna March 1943, Merten akapiwa mutungamiri we24th U-boat Flotilla. Muna February 1945, akaendeswa kuFührer Headquarters muBerlin. Pakupera kwehondo, akaitwa musungwa wehondo nemauto eU.S. uye akasunungurwa zvakare mukupera kwaJune 1945. 