equipped tanks were referred to as Rhino Tank. After breaking out of the bocage, VIII Corps was able to roll fifty miles in seven days, but it, and the remainder of Bradley's First Army, remained bottled up on the Cotentin Peninsula. The next phase of the fight, codenamed Operation Cobra was to break out of the peninsula, and once this occurred, Patton's Third Army would join the fight. The operation began on 24 July 1944 when American air commanders were asked to lay a carpet of bombs on the Germans to soften them up for the advancing ground forces. Poor weather curtailed the operation on the first day, but more than a thousand bombing missions were carried out the following day. Lieutenant General Lesley McNair, chief of the Army Ground Forces, came to Middleton's headquarters to witness the bombing. Middleton warned him to stay at corps headquarters, but McNair strayed away far enough that he and other members of his party were killed when they got caught by a stick of Allied bombs. More than 600 U.S. troops were killed or wounded in this friendly fire incident when the bombs fell short of their intended target. Despite the mishap, the bombing was effective in reducing the German resistance, and over the next few days the VIII Corps was able to move south along the coast. On 30 July they seized the town of Avranches, the gateway to Brittany and southern Normandy. Once in command of Avranches, VIII Corps then secured the bridges at Pontaubault, and in doing so, broke out of the Cotentin Peninsula and into Brittany. This brought about the planned command change, and at noon on 1 Aug 1944 Omar Bradley moved up to command the 12th Army Group, Courtney Hodges took over the First Army, and Patton's Third Army was activated into the group along with First Army, with Middleton's VIII Corps now falling under General Patton. Following the breakout, Middleton found himself in a doctrinally uncomfortable situation, as the allies were now in a position to pursue the Germans. The cautious and methodical Middleton was in command of two infantry divisions and two armored divisions within his corps, and the impatient and audacious Patton could not understand why Middleton was not moving his armor quickly in pursuit. In early August Patton wrote in his diary, "I cannot make out why Middleton was so apathetic or dumb.