Rubuta ci gaba ga wannan sakin layi - Cowdin ya kasance colonel na 2nd Massachusetts Militia Regiment a farkon yakin, kuma an nada shi colonel na 1st Massachusetts Infantry a ranar 25 ga Mayu, 1861. Ya jagoranci rundunarsa a yakin Blackburn's Ford a ranar 18 ga Yuli, 1861, ya kasance wani ɓangare na brigade na Isra'ila B. Richardson na Division Daniel Tyler a yakin farko na Bull Run, inda aka kashe dokinsa. Ya kuma ga aiki a Williamsburg, Fair Oaks
, Glendale, Malvern Hill da kuma Chantilly.