Kammala jumla mai zuwa: An haife shi a Ogdensburg, New York, Chapin ya shiga soja daga Pamelia, New York a watan Fabrairun 1864 na tsawon shekara 1. Ya kasance yana aiki a cikin New York Volunteer Infantry na 142 lokacin da rundunarsa ta kai hari a kan jagorancin kungiyar ta Tarayyar Turai a kan garuruwan da aka kafa a kan iyakar.
Yaƙin na biyu na Fort Fisher, North Carolina a ranar 15 ga Janairu, 1865. Ko da yake yana da shekaru 17 kawai, Chapin ya ci gaba da ci gaba da jagorancin rundunarsa, kuma duk da mummunar mummunar mummunar wuta, ya yanke wa abokan gaba gaba, ya ba da damar abokansa su karya garkuwar da kuma samun nasara. An canja shi zuwa 169th New York Infantry a watan Yuni na shekara ta 1865, kuma ya fita tare da rundunarsa a watan da ya gabata.