Final answer:
Nixon improved diplomatic relations with the People's Republic of China and the Soviet Union through a policy of détente, ultimately leading to strategic advantages for the United States and efforts towards arms reduction.
Step-by-step explanation:
President Richard Nixon significantly changed foreign policy regarding the People's Republic of China and the Soviet Union by improving diplomatic relations. This strategic move was part of the broader policy of détente, which sought to ease Cold War tensions. Nixon arranged a series of secret meetings through his National Security Advisor, Henry Kissinger, leading to a landmark visit to Beijing in 1972. The resumption of relations between the U.S. and China was designed to isolate the Soviet Union and leverage their rivalry to America's advantage. The Nixon administration also worked towards relaxing tensions with the Soviet Union, culminating in the signing of the Strategic Arms Limitation Treaty (SALT).