Operation Cobra, launched at the end of July 1944, was designed to open a decisive gap in the German defenses facing the American forces in Normandy. General Omar Bradley, commanding the First US Army, decided to use aerial saturation bombing to destroy the German defenses and create a breach. An initial attempt on July 24th proved disastrous, as the bombers dropped some of their payload on the American front lines, killing or wounding 150 men. Despite this, the bombing continued the next day. For three hours, 1,500 B-17 and B-24 bombers pummelled the target, supported by medium bombers and fighter bombers attacking with napalm. The few, shell-shocked German survivors either surrendered without a fight or fled. Even so, fierce fighting continued as the Americans strove to open up a passage for the armoured vehicles. On 26 July, VII US Corps advanced ten kilometers after crossing the Coutances-Saint-Lo road. Cracks started to appear in the German front and it collapsed the next day. The American armored divisions swept southwards and westwards. Entire German units were encircled, while others simply fell apart.