Dearing was mortally wounded at the Battle of High Bridge during the Appomattox Campaign of 1865, making him one of the last officers to die in the war.

He joined the recently arrived Washington Artillery from New Orleans, Louisiana; and was commissioned as 2nd Lieutenant and drill instructor in the 3rd company.

He participated in the First Battle of Bull Run while being assigned to the 1st company as part of the 4th Brigade of Colonel Jubal Early in the Army of the Potomac, and served as volunteer aide to his battalion commander Major James B.

While his men were on the march Major Dearing rode ahead to the battlefield and offered his services to Lieutenant Colonel E. Porter Alexander of the corps reserve artillery.

Alexander, who's battalion supported the division of Major General Lafayette McLaws in its assault of the Peach Orchard, gave Dearing the command of two of his batteries.

[4] Those batteries, Jordan's "Bedford" and Woolfolk's "Ashland", were on the right of Alexander's line; and participated in the charge of Barksdale and Kershaw.

Inflicting heavy damage Dearing's batteries suffered from counter-battery fire, but stayed in position and was reinforced by numerous guns and sections on Col. Alexander's orders.

[7][8] In April 1864, while Dearing participated in the operations again New Bern and Plymouth, he was ordered back to the Army of Northern Virginia with his official rank of Lieutenant Colonel; to take command of its horse artillery.

He fought a close range pistol duel with the union commanders, Colonels Theodore Read and Francis Washburn.