Kammala jumla mai zuwa: Battalion ya fara zuwa Darwin a ranar 9 ga Afrilu 1941 kuma ya shafe watanni tara masu zuwa a kan horo da kuma aikin garuruwa; duk da haka, abubuwan da aka keɓe da rashin jin daɗi kuma an hana shirye-shirye ta hanyar rashin kayan aiki. Bayan da
Harin Jafananci na Malaya a ranar 8 ga Disamba bataliya ta shirya don motsawa, ta isa Ambon a ranar 17 ga Disamba a matsayin wani ɓangare na Gull Force. A karkashin umurnin Roach, Gull Force ya ƙunshi 2/21st Battalion da aka goyi bayan bindigogi na bindigogi, injiniyoyi da sauran makamai masu goyan baya tare da haɗin gwiwa na mutane 1,100. A halin da ake ciki, sojojin Netherlands East Indies a tsibirin sun kai kimanin mutane 2,600, gami da kamfanonin sojojin Indonesia da na bakin teku na Dutch. An ba wa waɗannan sojojin aikin kare Bay of Ambon da filayen jirgin sama a Laha da Liang waɗanda ƙananan jiragen sama na Dutch da wasu jiragen saman Ostiraliya daga No. 13 Squadron RAAF ke amfani da su. Duk da haka tare da ƙananan sojojin Ostiraliya da Holland da suka kai mutane 3,700, Roach ya yi imanin cewa Ambon ba za a iya kare shi ba tare da iyakancewar kayan aikin soja da ake da shi kuma ya bukaci gaggawa. Daga bisani an cire shi daga umurninsa, kuma Lieutenant Colonel John Scott ya maye gurbinsa a ranar 17 ga Janairu, 1942. Kafin a sauko da Jafananci, Scott ya canza wurin da yawa daga cikin matsayinsa na tsaro, wanda ya haifar da bataliya ta kasance ba ta da shiri don kawar da mamayewar.