What decisive action did Truman take to end WWII in the Pacific?

The decisive action taken by Truman to end World War II in the Pacific was the atomic bombing of Hiroshima and Nagasaki. This action was significant as it represented the first and only use of nuclear weapons in warfare. On August 6, 1945, the United States dropped an atomic bomb on Hiroshima, followed by another bomb on Nagasaki on August 9, 1945. These bombings inflicted massive destruction and loss of life, leading to Japan's unconditional surrender shortly thereafter on August 15, 1945.

The rationale behind this decision was to bring a swift end to the war without the need for a costly invasion of the Japanese mainland, which was projected to result in substantial casualties on both sides. By employing this strategy, the United States aimed to demonstrate its military power and compel Japan to surrender. The bombings effectively expedited the conclusion of hostilities in the Pacific theater, resulting in the end of World War II.