By the beginning of August, more German reserves became available. The German forces were being encircled and the German High Command wanted these reserves to help with a retreat to the Seine. Hitler demanded an attack at Mortain on 7 August. The attack was pushed back by the Allies, who again had advance warning from Ultra code breaking. The original Allied plan was for encircling the Germans as far as the Loire valley. Bradley realized that many of the German forces in Normandy were not able to move by this stage and he got Montgomery's approval by telephone on 8 August for to encircle German forces. This was left to Patton to do. He moved nearly unopposed through Normandy. The Germans were left in near Chambois. Strong German defense and the sending of some American troops for an attack by Patton towards the Seine at Mantes prevented the Germans from being trapped until 21 August. On this date, 50,000 German troops were trapped.