FILE - Then U.S. President Richard Nixon and first lady Pat Nixon enter the palace grounds of Beijing's Forbidden City as heavy snow falls on Feb. 25, 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)