Mainly the Soviet Union backed the Viet Minh otherwise known as the North Vietnamese as the USSR backed many communist/socialist countries around the world in small proxy wars against the United States to try and gain influence and expand communism. So your answer would be the Union of Soviet Socialist Republics.
As the initial communist state, the Soviet Union encouraged North Vietnam, with gaining support in the late 1960s. While the U.S.S.R. granted some units, their fullest grant was in weaponry.
Explanation:Hope i could help!Stay safe and drink water<3
