What two things did the United States do to turn the war in favor of the Allies in the Battle of the Atlantic?

The outcome of the battle was a strategic victory for the Allies—the German blockade failed—but at great cost: 3,500 merchant ships and 175 warships were sunk in the Atlantic for the loss of 783 U-boats (the majority being Type VII submarines) and 47 German surface warships, including 4 battleships/

Brainliest?