Kammala wannan jumla: O'Bannon ya shiga Rundunar Sojan Ruwa a ranar 18 ga Janairu, 1801. A matsayinsa na laftanan farko da aka sanya wa, ya ba da umurni ga rundunar sojan ruwa bakwai da masu kula da sojan ruwa biyu a cikin karamin rundunar jakadancin diflomasiyya Janar William Eaton (1764<unk>1811) yayin yakin Tripoli na Yaƙin Barbary na Farko (1801<unk>1805). A cikin ayyukan haɗin gwiwa tare da Sojojin Ruwa na Amurka, ya jagoranci nasarar kai hari a
Yaƙin Derna, wani gari mai gabar teku a gabashin Libya ta zamani a ranar 27 ga Afrilu, 1805, yana ba wa Marines 'Hymn layinsa "zuwa gabar tekun Tripoli". Lieutenant O'Bannon ya zama mutum na farko da ya ɗaga tutar Amurka a ƙasar waje a lokacin yaƙi; O'Bannon na sama, William Eaton (1764<unk>1811), tsohon jami'in Soja, ya ɗaga tutar Amurka watanni da yawa da suka gabata yayin tafiya a kan Kogin Nilu daga Alexandria zuwa Alkahira, amma ba a lokacin yaƙi ba. Dangane da almara na Marine Corps, Hamet Karamanli ya burge da ƙarfin zuciyar O'Bannon har ya ba shi takobin Mameluke a matsayin alamar girmamawa.