human
The United States was the first nation to develop nuclear weapons through the Manhattan Project during WWII. The U.S. then demonstrated its nuclear power by using two atomic bombs against the Japanese to bring WWII to an end. 

Nuclear Weapons are extremely powerful weapons that can destroy cities and kill thousands of people. The power for a nuclear weapon comes from the splitting or fusion of atoms that releases an enormous amount of energy. 

The Soviets were thought to be far behind in developing a nuclear weapon, but a number of spies working in the top-secret Manhattan project stole the designs, leading to a much accelerated Soviet Nuclear program.  The U.S. was shocked when the Soviets successfully tested its first atomic bomb on August 29, 1949. 

After the Soviet Union had developed their atomic bomb, the two countries entered into an arms race. Each nation tried to build up better and  more weapons that the other in order to remain the more powerful nation. 

Why did the United States. & Soviet Union begin an arms race?
gpt
--- Reasoning ---
1. Is the question multiple-choice question?
No
2. Is it implied multiple-choice question?
No
3. If two experts were independently asked the question, will the final answer be exactly the same?
No

--- Answer ---
open