Hancock's assault started at 4:35 a.m. on May 12 and easily crashed through the Confederate works. Despite the initial success at obliterating much of the Mule Shoe salient, there was a flaw in the Union plan—no one had considered how to capitalize on the breakthrough. The 15,000 infantrymen of Hancock's II Corps had crowded into a narrow front about a half mile wide and soon lost all unit cohesion, becoming little more than an armed mob. Following the initial shock, the Confederate leadership at all levels began to react well to the Union onslaught and reinforcements were rushed in to stem the tide.