WASHINGTON — On Sunday, June 25, 1950, the Korean People's Army attacked across the 38th parallel, captured Seoul — capital of the Republic of Korea — and began driving south. The battered South Korean army and their U.S. military advisers quickly were pushed into the "Pusan Perimeter" on the southern tip of the peninsula — and U.S. President Harry Truman took the case to the United Nations Security Council. American leadership and the absence of the Soviet ambassador resulted in swift passage of Security Council Resolution 84. The measure — perhaps the last time in history that the U.N. acted...