By the end of world war ii, the united states and russia were allies. why did tensions increase between the soviet union and the united states after the war? a. the soviet union had established communist control, and the united states wanted to limit the spread of communism. b. the united states felt that it carried much of the financial burden of world war ii. c. the soviet union made secret alliances with germany. d. the soviet union used money that should have been used to pay reparations and wartime debts for the building of nuclear arms.