Answer:
United States and the Soviet Union.
Explanation:
The Soviet Union was trying to spread communism all over Korea. The United States joined in with South Korea to fight against the communist North Korea.
The correct answer to this open question is the following.
We are talking about the Gulf of Tonkin Resolution. This resolution changed the rules of war as outlined in the U.S. constitution. With this resolution, the US Congress granted the President of the United States -in this case, Lyndon B. Jhonson- unlimited powers to stop communism in Vietnam. After the aggression of two US navy vessels stationed in the Gulf of Tonkin, Congress passed the resolution on August 7, 1964. From this point on, the US Army committed to total support of South Vietnam in the Vietnam War.