In 1942 the Allied powers faced the most serious challenge to their control of the seas encountered in the Second World War: the menace of the U-boat. Fast, well-armed, and long-ranged, Hitler's submarines attacked shipping throughout the North Atlantic, often within sight of America's coastal towns and cities. Eventually, the combination of intelligence, land and seabased air power, and surface vessel operations from both North American and British bases ended this threat, making possible the Allied build-up for the invasion of Europe in 1944. This booklet, by A. Timothy Warnock of the Air Force Historical Research Agency, is one of a series tracing selected Army Air Forces activities in the Second World War. It describes the Army Air Forces' contribution to the Battle of the Atlantic from the American Theater. A subsequent booklet will examine the campaign in the eastern Atlantic and the Mediterranean. Flying radar-equipped long-range patrol planes, AAF airmen demonstrated the value of land-based air power against naval threats. This success has been reaffirmed consistently since the Second World War, from Vietnam and crises such as the Mayaguez incident to operations in Desert Shield and Desert Storm. The Harpoon-armed B-52s of our present-day global Air Force are the heirs of a sea-control tradition dating to the AAF's A-29s and B-24s of the Second World War.