As commander of an infantry regiment, Gibbs participated in the successful defense of Suffolk, Virginia and Norfolk, Virginia, in April and early May, 1863 when Confederate forces under Lt. Gen. James Longstreet tried to retake those key locations. He led his brigade or his regiment in major battles of the Overland Campaign and Maj. Gen. Philip Sheridan's raid which led to the Battle of Yellow Tavern. His brigade and division were detached from the Army of the Potomac soon after the beginning of the Siege of Petersburg in order to serve with Sheridan in all the battles of the Shenandoah Valley Campaigns of 1864. He and his brigade returned to Petersburg with Sheridan on March 26, 1865, and played a large part in the key battles of Dinwiddie Court House and Five Forks, which led to the breaking of the Confederate lines and the flight of the Confederate Army of Northern Virginia under the command of General Robert E. Lee from Petersburg and Richmond, Virginia. His brigade and division, under the command of Brig. Gen. Thomas C. Devin and the overall command of Maj. Gen. Sheridan joined in the pursuit of the Army of Northern Virginia in the ensuing Appomattox Campaign, and were engaged especially at the key Battle of Sayler's Creek (sometimes shown as "Sailor's Creek"). Gibbs was present at the surrender of the Army of Northern Virginia at Appomattox Court House on April 9, 1865.