He commanded an Ohio regiment and, frequently, a brigade, during the war, and played a role in the defense of Culp's Hill during the July 1863 Battle of Gettysburg.

He joined the United States Army on May 14, 1850, as an enlisted man with the rank of private and subsequently served in a wide variety of garrisons and outposts.

[2] Following the outbreak of the Civil War and the firing on the Union garrison at Fort Sumter in Charleston Harbor, Candy was appointed on September 21, 1861, as a captain and assistant adjutant general of volunteers.

XII Corps was in reserve during the Battle of Fredericksburg, but it participated in Maj. Gen. Ambrose Burnside's Mud March.

He commanded the same brigade at the Battle of Gettysburg, arriving on the Baltimore Pike, behind the Union right, late on the first day of the fight (July 1, 1863).

Late in the day, Geary led the brigades of George S. Greene and Candy to Little Round Top to protect the Union left flank.

Candy was mustered out of the volunteer service on January 14, 1865, and he received a brevet appointment as a brigadier general on March 13, 1865.