The biggest nuclear challenge toward U.S. security strategy currently comes from Russia, China and North Korea. They have been exposed on not only nuclear potential but also nuclear terror possibility. Still Russia’s nuclear weapons exceed the U.S. in numbers and sizes. As well, China’s nuclear technique shave been developed in incredible speed. Its nuclear ambition is now reaching the cosmos beyond the limit of time and space over the globe. Beside, North Korea is on the top possibility of nuclear terror attacks among three countries that it never stops the ventures as its number one national military strategy. North Korea can provoke nuclear terror or nuclear war toward any country in the international society no matter what its national interests exist. If North Korea fires ICBM(Inter-Continental Ballistic Missile) loaded with nuclear warhead, most possible among three countries, it will seriously sweep away international security in danger in a moment. This book deals with U.S. security strategy to beat up three former communist countries; Russia, China, and North Korea’s variable nuclear terror aspects based on nonproliferation.