He emerged as the outstanding cavalry leader on the Union (Northern) side in the American Civil War, distinguishing himself in Tennessee and in the Chattanooga Campaign (November 1863) before being appointed in April 1864 to command the cavalry of the Army of the Potomac. His campaign in the Shenandoah Valley (September–October 1864) laid waste one of the south’s most important supply regions, while his victory at Five Forks on 1 April 1865 effectively forced Robert E. Lee to abandon Petersburg and Richmond. After the war Sheridan commanded the 5th military district in the South, and in 1884 he succeeded Sherman as commander-in-chief of the US Army.