Rubuta ci gaba ga wannan sakin layi - A watan Mayu 1861 ya shiga cikin 18th Illinois Volunteer Infantry Regiment, kuma an nada shi a matsayin babban jami'in farko. Lokacinsa a matsayin kwamandan rundunar a Kentucky da Tennessee ya kasance mai rikitarwa da kuma "ordeal". Ya sha wahala rauni a lokacin yakin Fort Donelson. A watan Nuwambar 1862 an ba shi izini a matsayin brigadier janar, kuma ya umurci brigade a cikin Division na biyu na XIII Corps. Ya yi yaƙi da bambanci a cikin Kamfen na Vicksburg a 1863. Ya jagoranci mutanensa a yakin Port Gibson
, Champion's Hill, da Big Black River Bridge. kuma a lokacin babban hari na 22 ga Mayu, 1863 a kan Vicksburg MS, inda sojojin da ke ƙarƙashin umurninsa su ne kawai sojojin Tarayyar da suka shiga ayyukan Confederate a Railroad Redoubt inda suka dasa tutar Amurka.