After the United States' entry into the Second World War in 1941, their war department realised that, due to the increasing dominance of air power, their troops would need some help identifying the aircraft active in the various theatres of the war, whether friend or foe. Indeed, determining friend from foe quickly was key to survival. The result was this guide, produced for the US Armed Forces, and intended for concentrated study by their members. It considered all possible angles that the aircraft might be seen from, depending on which particular force was using the manual, and the result is a well-rounded guide to the aircraft that flew in the Second World War, a vital resource then, and a fascinating insight now.