Rubuta ci gaba ga wannan sakin layi - A lokacin yakin basasar Amurka, Crandall ya ba da sabis don taimakawa marasa lafiya da rauni daga yakin Fair Oaks
da kuma yakin Fredericksburg. Ganin yanayin da ke wurin ya sa ya yi imani da wajibcin aika da jami'an kiwon lafiya don taimakawa wadanda suka ji rauni, kuma a taron 1863 na New York State Medical Society ya ba da shawarar ƙuduri don nada jami'in likita zuwa Washington don kula da marasa lafiya da raunuka na New York. An gabatar da ƙudurin ga Gwamna da Majalisar Dokoki kuma sun wuce. Lokacin da 'yan uwansa biyu suka ji rauni a wajen Atlanta a 1864, ya zo ya taimaka musu kuma ya yi aiki a asibitocin Nashville da Louisville na makonni da yawa. An nada shi Surgeon na 141 na New York Volunteer Infantry, tare da kuri'a daya daga cikin jami'an kungiyar. Kamar yadda kawai aka sake zabar shi don sake zaben majalisar dokokin jihar, ya ƙi. A watan Afrilu na shekara ta 1865, Gwamna Fenton ya nada shi wakilin sojan New York a City Point, Virginia. Ya kuma yi aiki a matsayin Wakilin Ziyarci na Asibitocin Soja kuma ya yi aiki a asibitoci daban-daban na Ma'aikatar Potomac.