Hare served during the Mexican-American War in the 1st Indiana Volunteers 1846 and 1847.

After returning from the war, many of the men in the unit reenlisted in the 5th Indiana Volunteers.

Sullivan helped recruit and organize a three-months' infantry regiment, the 6th Indiana Volunteers.

During the Mexican-American War he served with the 5th Indiana Volunteers as a captain.

On April 16, 1861, he enlisted in Company E of the 9th Indiana Volunteers.

He was a captain in the 1st Indiana Volunteers from 1846 to 1847.

During the Civil War enlisted as a private in the Sixteenth Regiment, Indiana Volunteers.

Following these battles he was transferred to the 13th Indiana Volunteers as major and shortly after promoted to colonel on April 30, 1862.

During the war, he was commissioned as a chaplain with the 161st Indiana Volunteers, which served in Cuba for six months.

He enlisted in the ninth Indiana Volunteers as a second lieutenant in 1861.