The recent issue on the withdrawal of U.S. Forces from Korea Suggests an Urgency of Self Defense of Korea. The expected huge defense budget and her armed forces create a need for an operational analysis. It is shown through a statistical analysis what some of the opportunity costs of defense spending have been. Some evidences about what some of the economy sacrifice if defense spending rises have been analyzed to provide executive departments with a quantitative basis for decisions. The Korea-U.S. alliance is discussed in view of the developmental effects of U.S. aids and deterrent effects of U.S.F.K.