When the Army of the Potomac was reorganized preceding Lt. Gen. Ulysses S. Grant's Overland Campaign, Sweitzer retained brigade command in Griffin’s First Division. His brigade absorbed Tilton’s 22nd Regiment Massachusetts Volunteer Infantry. Sweitzer led the brigade at the Battle of the Wilderness and the Battle of Spotsylvania. Sweitzer distinguished himself at the Battle of North Anna, holding the exposed right flank of V Corps during a Confederate attack near Jericho Mills. He also commanded these troops at the Battle of Cold Harbor and the early stages of the Siege of Petersburg.