U.S. NATIONAL SECURITY STRATEGY AND THE DRASTIC CHANGE OF INTERNATIONAL STRATEGIC PATTERN Peng Guangqian（7） In the late 1980s and early 1990s, the national security strategy of the United States changed with the breakdown of the Yalta regime which had dominated the world for 40 years since the end of WWII. From President Bush to President Clinton, a new strategy with post-Cold War features gradually took shape. This readjustment of strategy, judging from both its scope and depth, has been most significant one since WWII.