The Battle of Opequon, also known as the Third Battle of Winchester, began in the morning on September 19, 1864. Some historians consider this the most important battle of the Shenandoah Campaign. Sheridan's Army of the Shenandoah defeated Early's Army of the Valley. Union casualties were about 5,000 out of 40,000 men, while Confederate casualties were about 3,600 out of 12,000 men. Generals and colonels on both sides were killed, including Confederate Colonel George S. Patton Sr.—grandfather of the famous World War II tank commander, General George S. Patton. Confederate General Robert E. Rodes was killed, and Confederate cavalry generals Fitzhugh Lee and Bradley Johnson were among the wounded. General David Allen Russell, killed in action, was among the Union casualties. The majority of the Union casualties were in the infantry. Averell's Second Cavalry Division had only 35 casualties, including four from the 1st West Virginia Cavalry.