Dee ihe na-aga n'ihu maka paragraf a - Mgbe Agha Obodo America malitere na 1861, Fesler kwụnyere Union. N'abalị iri atọ n'ọnwa Ọgọstụ, afọ 1861, o sonyere ndị agha Union na Morgantown, Indiana. E mere Fesler onye isi nke Company G na 27th Indiana Infantry Regiment. Fesler duziri ndị agha ya n'agha nke mbụ nke Winchester
na Agha Ugwu Cedar. Na 1862, e kenyere ndị Fesler's Regiment na 12th Army Corps, nke ọ ga-anọgide na 1863. Mgbe ahụ Fesler nyere ndị otu ya iwu n'oge Agha Antietam, nso Sharpsburg, Maryland, na Septemba 17, 1862. Ọchịchị ya nọrọ oge oyi nke 1862 ruo 1863 na-ama ụlọikwuu na Stafford Courthouse, Virginia, na February 13, 1863, Fesler kwalitere Lieutenant Colonel nke 27th Indiana. N'ọnwa Machị afọ 1863, e nyere 12th Corps, nke 27th Indiana so na ya, kpakpando dị ka akara nke ndị agha ya. Na Mee 5, 1863, Fesler merụrụ ahụ n'agha n'oge Agha Chancellorsville, na Spotsylvania County, Virginia. Mgbe ahụ, o nyere iwu nwa oge na 27th Indiana site na July 2-3, 1863 n'oge Agha nke Gettysburg mgbe a na-etinye onye isi ndị agha nke ndị agha ahụ n'ọchịchị nke ndị agha ya. Fesler na ndị agha ya sonyere n'ime ka ọgba aghara nke New York City Draft Riots kwụsị n'ọnwa ahụ.