The most important people in the war that served were "Robert E. Lee, William Tecumseh Sherman, P.G.T. Beauregard, Stonewall Jackson, Ulysses S. Grant, James Longstreet, George Meade, George McClellan and George Picket. Soldiers Engaged United States: 32,000 Soldiers and 60,000 militia Mexico: 35,000-60,000. Generals/Commanders United States: Zachary Taylor, Stephen W. Kearney and Winfield Scot Mexico: Antonio Lopez de Santa Anna, Mariano Arista, Pedro de Ampudia and Jose Maria Flores."