Attempting to profit from the two Union wings being separated by the Chickahominy River, and McClellan's indecisiveness in waiting for McDowell, Joe Johnson's numerically superior Confederates attempted to envelope and destroy the isolated Union left wing south of the river. Poor orders and staff control, however, meant that all coordination was lost, and the assault turned into piecemeal frontal attacks which were beaten off by the Yankee's causing more southern casualties than northern. Gen. Johnston himself was wounded by a shell fragment, causing Robert E Lee to be given command of the Army of Northern Virginia.