FILE - Then U.S. President Richard Nixon stands at The Great Wall of China, which snakes over the mountain behind him, near Beijing on Feb. 24, 1972. At the height of the Cold War, U.S. President Richard Nixon flew into communist China's center of power for a visit that over time would transform U.S.-China relations and China's position in the world in ways that were unimaginable at the time. (AP Photo, File)