The U.S. emerged as the most powerful nation and the only nuclear power from WW2. Shortly thereafter, The Soviet Union, another victor from WW2, stole America's nuclear secrets and bought some of the best minds Germany had to offer and became a nuclear power and the only equal to America. This started the Cold War. From then, both the US and the USSR competed on virtually every front, such as: space exploration, economics, nuclear prowess, and political influence with the world. Thus America and Russia became the only world powers. From the latter half of the 20th century, both powers heavily contributed to rapid advancements of science to out match the other. They also tried to stun the growth power of the other via proxy warfare.
