75th Anniversary of the Combined Bomber Offensive: American and British Forces Work Together to Attack German Industry from the Air

American military leadership knew that defeating Germany in World War II would require a complex strategy that included devastation of German industry. Beginning in 1942 American forces began the Strategic Bombing Campaign—an effort to attack German war industries from the air, and deplete access to resources, and supplies. The following year on June 10, 1943 the effort transformed into the Combined Bomber Offensive when American and British Forces came together to coordinate air attacks on German industry, such as aircraft and ball bearing factories, oil fields and rail lines.  

The British would increase attacks against area targets by night while American bombers would attack precision targets in daylight. While this offensive targeted destruction of German industrial capacity and civilian morale, it also drew German fighter squadrons away from the Eastern Front and the Mediterranean Theater. Even with this sound strategy, success in the Combined Bomber Offensive would not come easily. Intelligence gathering inside Germany was difficult. Because industrial capacity, bomb damage, or fighter losses were not sent encoded by radio, Ultra decryption offered no help.  Allied reconnaissance aircraft only gave a fragmentary picture of conditions. And American commanders believed bomber formations could operate without escort against fighters.

The Eighth Air Force tested new tactics and flying formations during this offensive. Col. Curtis LeMay developed a basic formation for bombers called the “combat box”. The B-17 “Flying Fortresses” and B-24 “Liberators” flew in tight groups so that an approaching enemy fighter would be vulnerable to gunners in multiple aircraft. These unescorted American combat box formations came out of necessity at the time. American fighters lacked the fuel endurance to accompany bombers to critical targets deep in mainland Europe.

In July and August 1943 the Eighth Air Force began a series of grueling attacks against ball bearing plants in Schweinfurt, Germany and aircraft factories in Regensburg, Germany.  American bomber units based in the Mediterranean committed to attacks on aircraft and oil production facilities in Austria and Romania. Because these bombers flew unescorted, losses became unsustainable. During this time period, estimates show that nearly 30 percent of bombers that hit targets went down with their crew. While American forces inflicted significant damage on German aircraft and fuel industries, these losses and incomplete intelligence prevented follow-up attacks that could have dramatically increased damage.

German ball bearing factories became the target in October 1943 during “Black Week.” Bombers were still flying unescorted and aircraft and aircrew losses continued to mount. The attacks damaged or destroyed about half of ball bearing production and drew more air defense forces back to Germany from occupied Europe.  Black Week success came at a high a price with losses around 25 percent. American bomber strategy had to change in order to continue.

By 1944 the Americans knew that bombers had to be protected by long-range fighter escorts. The new P-47 “Thunderbolt” and P-38 “Lightning” fighter aircraft were equipped with long-range fuel drop tanks, and fuel capacity was increased for the new P-51 “Mustang.” Gen. Jimmy Doolittle said “The first duty of Eighth Air Force fighters is to destroy German fighters.” Instead of sticking close to the bombers in a defensive mode, some escorts went on the offensive by attacking approaching German fighters or their airfields.

American bombing operations in 1944 improved dramatically from the previous year. Eighth Air Force bombers flew escorted by aggressive long-range fighters that devastated sluggish German “destroyer” units. The bomber force increased in size and added the Fifteenth Air Force based in Southern Italy. And American forces began focusing more on defeating the German fighter force in the air. Subsequently, Germany required more air defense reinforcements from battlefronts and occupied Europe. German losses in fighter aircraft and pilots mounted decisively. Replacement fighter pilots lacked experience and their training was reduced by fuel shortages. The war was far from over, but occupied Europe was becoming a “fortress without a roof."