Tuhia he tomokanga mō tēnei wāhanga - I muri i te whakawātea i a Missouri mō te ngahuru me te hotoke, ka honoa te 18 o Indiana ki te ope a Grant e ngana ana ki te whakawhiti i te awa o Mississippi me te hopu i a Vicksburg. I whawhai te 18 Indiana ki Port Gibson
I uru ia ki nga mahi whakapae a tawhio noa a Vicksburg, i reira i whakahau ai ia i tetahi pirihimana i whakamoemitihia mo nga mahi maia i te wa o te whakaekenga tuatahi ki te pa kaha o te hoariri i te Mei 1863. Whai muri i te mutunga angitu o te mahi Vicksburg, i noho tonu a Washburn ki te XIII Army Corps i uru ki nga mahi i runga i te awa o Teche, me te angitu o te hopu i etahi o nga puni Rebel. I te marama o Hanuere 1864, i tukuna te 18 o Indiana ki Virginia i reira i uru ai ki etahi pakanga pakeke. I te marama o Akuhata 1864, i whakauruhia te 18th Indiana ki te 4th Brigade, 2nd Division (Grover) o Emory's XIX Army Corps.