Who sent troops to south korea in 1950?

Harry Truman

Explanation:

In 1948, through the Korean War, two autonomous states were constituted: the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea). The following year, most foreign troops withdrew from both countries.

Northern Communist forces repeatedly attacked and invaded South Korea on June 25, 1950. Two days later US President Harry S. Truman sent troops to South Korea, although without congressional authorization to declare war. The objective of the American troops, was to swear South Korea to defend its territory.