Complex sentence: Colonel Richard Owen took over as commandant of the prisoner-of-war camp and served in that role until June 20,1862, when his regiment was called to active duty and he departed Indianapolis with his men.
Split into simpler sentences: Colonel Richard Owen took over as commandant of the prisoner-of-war camp. Owen served as camp commandant until June 20,1862, when his regiment was called to active duty and Owen departed Indianapolis with his men.