Why did the United States decide to get involved in the Korean War? to colonize the Korean peninsula
to continue its war against Japan
to contain the spread of communism
to gain a presence in Southwest Asia

The answer is to contain the spread of communism.

Explanation:

The Korean War (1950-1953) was the first military action of the Cold War. It was sparked by the June 25, 1950 invasion of South Korea by 75,000 members of the North Korean People’s Army. The line they crossed, the 38th parallel, was created in 1945 to separate the Soviet-supported Democratic People’s Republic of Korea (today’s North Korea) and the U.S.-supported Republic of Korea to the South. The Korean War was a civil conflict that became a proxy war between superpowers clashing over communism and democracy. Between 2 and 4 million people died, 70 percent of them civilians.

The United States became involved in the Korean War because onn August 29, 1949, the Soviets detonated their first atomic bomb. Klaus Fuchs, a physicist who had helped the United States build its atomic bomb program, had leaked the blueprint of the “Fat Man” atomic bomb to the Soviets. The revelation stoked Cold War paranoia. Then, on October 1, 1949, communist revolutionary Mao Zedong announced the creation of the People’s Republic of China following the defeat of the U.S.-supported Chinese nationalists led by Chiang Kai-shek.

On April 14, 1950, Truman received a document called National Security Council Paper Number 68 (NSC-68). Created by the Defense Department, the State Department, the CIA, and other agencies, it advised the president to grow the defense industry to counter what these agencies saw as the threat of global communism. The recommendations cemented Truman’s next move. On June 27, 1950, President Truman ordered U.S. forces to South Korea to repulse the North’s invasion.

the tariff was created to protect industry in the northern part of the united states. industries in the north were being driven out of business by imported goods that were priced at a low rate. the goal was to protect these industries   by taxing the goods.