Rubuta ci gaba ga wannan sakin layi - A lokacin da yakin basasa ya barke, Capehart ya bar aikin likitancinsa a Bridgeport kuma ya ba da kansa ga rundunar Union. An nada shi likitan likitancin na 1st West Virginia Cavalry a ranar 18 ga Satumba, 1861. A cikin rabin rabin 1863, ya shiga cikin yakin Gettysburg, Bristoe Station, da kuma Mine Run
Ka yi haƙuri. Bisa ga shawarwarin Janar Judson Kilpatrick da sauransu, Capehart ya zama colonel kuma ya yi nasara da Nathaniel P. Richmond, wanda ya yi murabus saboda matsalolin kiwon lafiya, a matsayin kwamandan rundunar a ranar 22 ga Fabrairu, 1864.