In Russian army was … by the idea of creating huge planes. At that times they were proposed to have as much propellers as possible to help carrying those huge flying fortresses into the air, jet propulsion has not been implemented at those times yet.
The Kalinin was a heavy experimental aircraft designed and tested in the Soviet Union in the early It was of unusual configuration with twin booms and large underwing pods housing fixed landing gear and machine gun turrets.
Kalinin K-7 Giant Transport/Bomber (USRR 1933) Designed by World War I aviator Konstantin Kalinin with a wingspan greater than the B-52 and a much greater wing area, the K-7 was one of the biggest aircraft built before the jet age. It was only one engine short of the B-52 as well, having the curious arrangement of six pulling on the wing leading edge and one pushing at the rear. http://www.fiddlersgreen.net/models/aircraft/Kalinin-K7.html