Aaron B. Henry enlisted in the 4th Regt Cavalry Missouri State Militia Company H on April 9th, 1862 in Stewartsville Missouri, enlisting officer was Messimer. He mustered out on April 28th, 1865.

The 4th Regt Cavalry MSM served in Western and Central Missouri they seem to have been active in the Mine Creek, Little Osage area during the raid of 64.