[1] After the Mexican War Cloud returned to Ohio and served in a local militia company, the Columbus Videttes, in which he was elected captain.

With the outbreak of the Civil War, Cloud enlisted in the 2nd Kansas Infantry as major and distinguished himself at the battle of Wilson's Creek.

After his infantry enlistment expired, Cloud organized the 2nd Kansas Cavalry in 1862, and was commissioned major of the regiment.

He commanded a brigade in James G. Blunt's division at the battles of Old Fort Wayne, Cane Hill and Prairie Grove.

Cloud reverted to regimental command and fought at Honey Springs and was the senior Union officer on the field at the battle of Devil's Backbone.