Tupolev Tu-4
In 1945, three B-29s were forced to land in Soviet territory after a bombing raid on Japan because of a lack of fuel. Since the Soviet Union was not at war with Japan at the time, the aircraft and crews were interned. Eventually, the B-29 crew members were returned, but the aircraft remained in Russian hands. Seeking a modern long-range bomber, Joseph Stalin ordered the Tupolev OKB to reverse-engineer the Superfortress.
The resulting aircraft first flew on May 19, 1947 and immediately began series production. Although largely identical in appearance to American B-29's the Tu-4 (Nato reporting name: "Bull"), had Soviet-designed defensive guns and had been re-engineered to suit production using metric tools; resulting in an aircraft that was slightly heavier and slower than the B-29. The Tu-4 presented a significant leap forward in Soviet strategic bombing. Not only did the Red Air Force have the means to deliver nuclear weapons, but Tu-4 had sufficient range to reach the United States on a one-way trip. On October 18, 1951, a Tu-4 was used in the first air-drop test of a Soviet atomic bomb.
In Soviet service, the Tu-4 had been phased out of service by the early 1960s, being replaced by more modern aircraft such as the Tupolev Tu-95. Although the "Bull" never dropped a bomb in anger, the Tu-4 influenced Soviet aircraft technology, particularly airframe construction and onboard systems. The People's Liberation Army Air Force of China is rumoured to still operate up to 15 upgraded Tu-4s, possibly as AWACS platforms.
Advanced transport and bomber variants of the Tu-4 design such as the Tu-70, 75, 80, and 85, were developed and built, but none of these achieved serial production.
Read more about this topic: Boeing B-29 Superfortress Variants