Breakout into Brittany
Middleton’s 8th Corps, now under the Third Army, turned west from Avranches and entered Brittany. One armored division drove to Rennes and then to Lorient, another armored division drove to Brest, and an infantry division moved to St.-Malo. The entrance of American troops into Brittany chased the Germans into these port cities, as well as St.Nazaire and Nantes, which Hitler had designated as fortresses to be held to the last man. While small American forces contained the Germans in the port cities, siege operations got under way at St.-Malo, which was finally captured on August 17. The 8th Corps then moved to Brest and initiated siege operations on August 25. A fierce battle at that city finally ended on September 18. Meanwhile, headquarters of the United States Ninth Army, under Lt. Gen. William H. Simpson, had been committed in Brittany in order to provide control over operations that were increasingly farther behind the main front.
Though operations in Brittany had been undertaken with the object of gaining the port cities as points of entry for additional troops and supplies coming directly from the United States, the strong German defenses at St.-Malo and Brest and the accompanying destruction of the port facilities prompted a change in Allied plans. Not only did the Allies decide not to rehabilitate the destroyed port cities; they also decided not to commence constructing the port complex at Quiberon Bay, the project code named Chastity, for by this time Brittany was far removed from the main stage of operations. Early in August, the main Allied armies had swept eastward from Avranches.