Kammala wannan jumla: An haifi Duncan Mansfield a watan Fabrairun 1778 a Albany, New York. Ya shiga cikin Rundunar Sojan Ruwa ta Amurka a Philadelphia, Pennsylvania a ranar 11 ga Agusta 1798 kuma ya yi aiki har zuwa 1805. Yayin da yake aiki a kan schooner a lokacin
Yaƙin Barbary na Farko, Sergeant Mansfield ya ba da gudummawa don aikin binciken da Lt. Stephen Decatur, Jr., ya jagoranci, 16 Fabrairu 1804. Lieutenant Decatur da ma'aikatansa 84-mutum sun yi tafiya ketch, wanda aka ɓoye a matsayin jirgin ruwa na Larabawa, a cikin Tripoli Harbor don halakar da jirgin ruwan Amurka da aka kama kwanan nan kuma ya hana amfani da ita a kan Amurka.