What action did President Truman take against Douglas MacArthur during the Korean War?

The correct answer is that President Truman removed Douglas MacArthur from command during the Korean War. This decision stemmed from a series of conflicts between Truman and MacArthur regarding military strategy and the conduct of the war. MacArthur, who was leading U.N. and American forces in Korea, advocated for expanding the war beyond the Korean Peninsula, including potentially attacking China, while Truman sought a more restrained approach to prevent a wider conflict that might involve the Soviet Union.

Truman's removal of MacArthur was significant as it highlighted the tension between civilian control of the military and military leadership. This action served to reinforce the principle that elected officials ultimately hold authority over military decisions. Truman's decision to relieve MacArthur was controversial and met with mixed public reaction, but it underscored the importance of maintaining a unified strategy in the Cold War context, where global tensions were high.