Ko te timatanga o te American Civil War i aukati i te maatauranga o Corson i a ia e whakauru ana ki te Kamupene K o te 4th Pennsylvania Infantry i te Paenga-whāwhā 1861, a ka whakauruhia hei kaitiaki i te Hurae 1861. I te hokinga mai ki Penn i te mutunga o taua tau, i mahi ia hei kaiako hauora i te hohipera ope i runga i Cherry me Brad Streets i a ia e ako ana i te kura. I whakauruhia ia ki te 6th Pennsylvania Reserves (35th Pennsylvania Volunteers) hei kaiawhina taakuta i te Poutu-te-rangi 1863 i muri i tana tohu i te tohu MD, i uru atu ki nga Pakanga o Gettysburg, Waipuke Waipuke, Manassas Gap, Bristoe Station, Mine Run
, Te Teihana o Rappahannock, Te Moana-a-Kiwa, Spotsylvania, Te Raki o Anna, me te Hahi o Bethesda. I whakawhiwhia ki a major mo te wehewehe i a ia ano i te Wildness, i whakahoutia ano a Corson i te Pipiri 1864. I te teihana o Bristoe i te Oketopa 14, i whakaorangia e Corson me tetahi kaitohutohu o te hohipera tetahi hoia i whara kino i mahue i waenga i nga raina i raro i te pupuhi a te Confederate. Mo tenei mahi, i whakawhiwhia ia ki te Tohu Tohu i te 13 o Mei 1899. I te marama o Noema 1864, ka noho ia hei kaitiaki hauora i Camp Discharge, i whakamahia hei kohikohi hoia, i Philadelphia.