Rubuta ci gaba ga wannan sakin layi - A shekara ta 1861, a lokacin da yakin basasar Amurka ya barke, Twitchell ya shiga cikin kamfanin I, 4th Vermont Infantry. Bayan da rundunar ta isa Washington, DC don yin aikin tsaro da kuma kammala horo a shirye-shiryen yaki, an sanya Twitchell a matsayin sakataren kamfaninsa. An ci gaba da shi zuwa ga Corporal, Sergeant, da kuma na farko Sergeant. Ya shiga cikin Siege na Yorktown a 1862, kuma ya ji rauni sau uku a yakin Lee's Mill, amma babu wani abu mai tsanani. Ya shiga cikin ƙarin fadace-fadace tare da 4th Vermont, ciki har da Battle of Savage Station
da kuma yakin kwana bakwai.