Whakaotihia te rerenga e whai ake nei: I te tīmatanga o te Pakanga ā-Iwi i te tau 1861, i mahi a Smith hei kaitiaki o te puni ki te Kawana o Illinois a Richard Yates. I te Hakihea 26, 1861 i tohua ia hei koroneela o te 45th Illinois Volunteer Infantry Regiment, me te taumata i hoki mai ki te Hurae 23, 1861 hei whakakapi i te Koroneela o mua i whakarere i tana Komihana kawanatanga i te wa i uru mai ai te rerenga ki te ratonga Federal. I arahina e ia tana pu i nga pakanga o Fort Henry, Fort Donelson me Shiloh. I te Noema 29, 1862 i whakatairangahia ia ki te rangatira rangatira o nga U.S. Volunteers. I whakahau poto ia i tetahi parirau i mua i te tango i te whakahau o te 8th Division, XVI Corps. I te wa i timata ai a Ulysses S. Grant i tana pakanga whakamutunga ki a Vicksburg, i tukuna a Smith ki te rangatira o te 1st Brigade, 3rd Division, XVII Corps. I whawhai ia i nga pakanga o
Ko Port Gibson, ko Raymond, ko Champion Hill, me ngā whakaeke ki Vicksburg. I te marama o Hune, 1863, i waenganui i te whakapae o Vicksburg, i whiriwhiria a Smith hei whakakapi i a Gen. Isaac F. Quinby hei rangatira mo te 7th Division, XVII Corps i muri i te mate o Quinby me te wehe atu. I te marama o Hepetema, 1863 i whakawhitihia a Smith ki te whakahau i te 2nd Division, XVII Corps me tana wehenga i tukuna me William T. Sherman ki te awhina i te awhina o Chattanooga. I te pakanga o Missionary Ridge, i uru a Smith ki nga whakaeke ki te taha matau o te Confederate i Tunnel Hill.