http://www.fas.org/nuke/guide/russia/bomber/tu-4.htm ~ we are not talking about the most technologically sophisticated planes here, but check out the quantities ~ 12,000!
10,000 to 12,000 aircraft of all types at the outbreak of World War II
IIRC, they're 4 engine prewar bombers were Bi and or Tri-planes. The Germans roached probably 70+% of all existing Soviet aircraft in the first 2 months of the war.
The Tu-4 Bull (B-29 copy) went into post WWII service.