Once the army became operational, it did not take Patton long to engage in the hard-driving cavalry tactics that he loved best. The Third Army was able to break out of the French hedgerow country and by August 20 had entered Argentan just southeast of Falaise. The only part of Third Army that was tied down was the XV Corps fighting against the tough German defensive positions in Brittany.

On August 25, the 80th Division began its move to eastern France with an advance of 280 miles in one day. The division then concentrated around Collemieres and two days later crossed the Seine, Aube, and Marne Rivers. By the end of August, the XII Corps had advanced to the high ground east of the Meuse River near St. Mihiel. This place had special significance for Patton because he had been wounded there during World War I.