After the Bomb

The world watched in awe as the first nuclear weapons exploded over Japan, but wonder soon turned to desire. Government leaders quickly realized the power of this new technology, and it wasn't long before countries like Britain, France, the USSR, and China had their own bombs.
Cold War

Although they were on the same side in World War II, the United States and the Soviet Union turned against one another almost immediately after the war was over. Since both sides had built up enough nuclear weapons to completely destroy the other, they avoided fighting each other directly. This type of war was known as a "Cold War."
The End of Humanity?

During the second half of the 20th century, people all over the world feared that human life on Earth might be wiped out in a nuclear war. Even though the Cold War is over, many nations still have nuclear weapons, and still more are working to build their own.
Question
How has the Manhattan Project affected our understanding of war?