The act that the US was upholding when they joined South Korea in fighting the war against North Korea was C. Truman Doctrine.
What was the Truman Doctrine?
The Truman Doctrine or the United States' foreign policy of containment, was part of President Harry Truman's efforts to provide political, military, and economic aid to democratic countries under communist threats or influences.
The purpose of the Truman Doctrine was to curtail the spread of communism.
Explanation:
Answer Options:
a. Monroe Doctrine
b. Patton Doctrine
c. Truman Doctrine
d. MacArthur Doctrine
Thus, the act that the US was upholding when they joined South Korea in fighting the war against North Korea was C. Truman Doctrine.
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