The Battle of Port Republic was fought on June 9, 1862, in Rockingham County, Virginia, as part of Confederate Army Maj. Gen. Thomas J. "Stonewall" Jackson's campaign through the Shenandoah Valley during the American Civil War. Port Republic was a fierce contest between two equally determined foes and was the most costly battle fought by Jackson's Army of the Valley during its campaign. Together, the battles of Cross Keys (fought the previous day) and Port Republic were the decisive victories in Jackson's Valley Campaign, forcing the Union armies to retreat and leaving Jackson free to reinforce Gen. Robert E. Lee for the Seven Days Battles outside Richmond, Virginia.