What sets the Civil War apart from all other American military conflicts is that many of the opposing officers knew each other. They had studied together at West Point, fought side by side in the Mexican War, and had even been friends. At the First Battle of Manassas, for example, Pierre G. T. Beauregard, who was second in the class of 1838 at West Point, battled Irvin McDowell, who had graduated twenty-third in the same class.