What precedent did president truman set when he sent troops to korea?

The President could send U.S. troops overseas without a congressional declaration of war.

On June 27, 1950, President Harry S. Truman announces that he is ordering U.S. air and naval forces to South Korea to aid the democratic nation in repulsing an invasion by communist North Korea.  

Harry S, Truman  was the 33rd president of the United States from 1945 to 1953, succeeding upon the death of Franklin D. Roosevelt after serving as vice president.

i think the answer is b.