 On 25 July 1944 , following six weeks of attritional warfare along a stalemated front , American forces under Lieutenant General Omar Bradley mounted an attack code @-@ named Operation Cobra , which broke through the German defenses near Saint @-@ Lô . Almost the entire western half of the German front in Normandy collapsed , and on 1 August , American forces captured Avranches . With the capture of this town at the base of the Cotentin peninsula , and an intact bridge at Pontaubault nearby , the American forces had " turned the corner " ; the German front could no longer be anchored against the sea at its western end and American forces could advance west and south into Brittany . The U.S. Third Army , commanded by Lieutenant General George S. Patton , was activated the same day . Despite German air attacks against the bridge at Pontaubault , Patton pushed no less than seven divisions across it during the next three days , and units of his army began advancing almost unopposed towards the Brittany ports . 
