from 150 to 170 Confederate guns began an artillery bombardment that was probably the largest of the war. In order to save valuable ammunition for the infantry attack that they knew would follow, the Army of the Potomac's artillery, under the command of Brigadier General Henry Jackson Hunt, at first did not return the enemy's fire. After waiting about 15 minutes, about 80 Union cannons opened fire. The Army of Northern Virginia was critically low on artillery ammunition, and the cannonade did not significantly affect the Union position.