On April 4, 1862, the Union Army pushed through Magruder's initial line of defense but the following day encountered his more effective Warwick Line. The nature of the terrain made it difficult to determine the exact disposition of the Confederate forces. McClellan estimated that the Confederates had 15 to 18,000 troops in the defensive line.ORA 11(1), 12; compare with Magruder's February return of 15,900 in ORA 9, 49, online
