Since the Soviet Union was not at war with Japan until August, 1945, they confiscated all American aircraft that made emergency landings in Russia prior to that time.
A total of three B-29's were confiscated, all in 1944 (Ding How and Ramp Trap II were among them).The first Tu-4's were produced on-schedule in 1947, less than two years after the project began.
Its maiden flight was in May, 1947 and its first public display was on Aviation Day in August, 1947.
Several hundred copies of the B-29 were produced without license in the Soviet Union until 1949.The only major change was to redesign the Barbette for the NR-23 cannon.
http://en.wikipedia.org/wiki/Tu-4
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