Cold War
The Cold War (1947 - 1991) was the tense fighting between the United States and its allies and the Soviet Union (also called the USSR) and its allies between the end of World War II and the fall of the Soviet Union. It is called the "Cold" War because the Americans and the Soviet Union never actually fought each other directly. Instead, they attacked each other in conflicts known as proxy wars in which powerful countries fight a foreign war but do not send their own troops. Both sides built large militaries with many new weapons and advanced technology. They spied on each other and threatened each other.