Japan surrendered after the dropping of atomic bombs on Hiroshima and Nagasaki on August 6 and August 9, 1945. DMA member Charles Salmans points out that the B-29 was also essential to the defeat of Japan because the U.S. needed a way to deliver such bombs. No aircraft had that capability before the B-29 and the design of this aircraft was revolutionary, only to be superseded as a World War II technological achievement by the development of the atomic bomb itself. Under the pressure of war, both the design and production of the bomber took place concurrently, beginning in 1940. Major design and engineering modifications were still taking place through 1945 with air crew, in effect, becoming test pilots. The B-29 was a huge technological advance, the first aircraft with a pressurized cabin. It had three times the bomb load and twice the range of any other bomber at the time, made possible in part by a revolutionary wing design. But it required the most powerful engines ever built, and these were its Achilles heel. Furthermore, it was designed for high level, precision bombing before there was understanding of the high-altitude jet stream, which was at its most powerful at the latitude of Tokyo and which blew bombs off target. Thus, bombing was anything but precise. Consequently, General Curtis LeMay had to alter the tactics to low-level firebombing and in a single night a raid on Tokyo caused more civilian casualties than either of the atomic bombs.