Kammala jumla mai zuwa: A watan Yunin 1862, Jewett ya shiga rundunar sojojin Amurka don yin yaki a yakin basasa, kuma an ba shi izini a matsayin na biyu a cikin 9th Vermont Infantry. A ranar 3 ga watan Agusta, an kama shi, kuma ya kasance fursuna na Confederacy na kwanaki 25. An ci gaba da Jewett zuwa na farko a watan Mayu 1863. A lokacin hidimarsa, ya shiga cikin yaƙe-yaƙe na Harper's Ferry (Satumba 13 da 15, 1862), Newport Barracks (Fabrairu 2, 1864), gonar Chaffin (Satumba 29, 1864), da
Fair Oaks (Oktoba 27, 1864). Ya yi murabus a watan Nuwambar 1864, kuma ya koma Vermont.