New revised edition, updated and expanded. The Boeing B 29 Superfortress will be remembered as the device to have made use of atomic weapons in war action; were, in fact, this type of aircraft that dropped the atomic bombs on Hiroshima and Nagasaki to force Japan to surrender in August 1945. Apart from that, however, the Boeing B 29 was an excellent plane, with cutting-edge features, including towers with weapons maneuverable automatically remote and pressurized compartments for the crew. The American interest in a bomber capable of carrying a significant offensive load over long distances and at high speed back to Boeing XB 15, 1933. Although, in the second half of that decade, the interest for such a weapon dims, the Boeing continued to develop the design of similar projects, culminating in the model 341, which is believed capable of carrying a load of 2, 240 pounds (just over 1, 000 kg) of bombs with a flight range of 7, 000 miles (11, 265 km) at a speed of over 400 miles / h (644 km / h). However, with the outbreak of World War II in Europe and the possibility of a future American involvement in it, the US Army Aviation Corps (USAAC) monster again interest for any weapon that would put the United States in the possibility of bombing the enemy also at very great distances. So in February 1940, he was made the request of the "Hemisphere Defense Weapon" (weapon for the defense of the hemisphere), and that of a bomber capable of carrying 2, 000 pounds (907 km) of bombs over a distance of 5333 miles (8, 600 km) at a speed of 400 miles / h (644 km / h). The bomber was supposed to also have tanks autostagnanti, a good armored protection, a heavy defensive armament and a chance to carry 16, 000 pounds (7, 250 kg) of offensive load.