Rubuta ci gaba don wannan sakin layi - Fara aikinsa a matsayin ɗan takara, Hanneken ya yi aiki a Yaƙin Banana na shekarun 1910 da 1920. A lokacin da Amurka ta mamaye Haiti
, ya kashe shugaban adawa Charlemagne Péralte, wanda aka ba shi lambar girmamawa. Daga baya, an ba Hanneken wani kwamiti, ya yi aiki a Haiti na wasu watanni kuma an ba shi lambar yabo ta Navy don kashe wani shugaban 'yan tawaye. Ya karbi Gicciye na Navy na biyu don ayyukansa a lokacin mamayar Nicaragua a ƙarshen 1920s.