Nuclear weapons are used for many different reasons. Some countries develop nuclear weapons and sell the information to other countries. Nuclear weapons can be used for a country to gain recognition. Still other countries use them to present a threat to another country or to show their power. Four countries in Asia: China, India, North Korea, and Pakistan either use nuclear weapons for one of these purposes or could in the future. Nuclear weapons have led to greater tensions between not only some Asian countries but also many other countries around the world.
The age of nuclear weapons really began when the U.S. used two atomic bombs on Japan at the end of World War II. The first bomb was dropped on the city of Hiroshima on August 6, 1945. The second bomb was dropped three days later on August 9, on the city of Nagasaki . These actions resulted in many thousands of deaths and the surrender of Japan. This was the first time that weapons of mass destruction were ever used. Many people were horrified by the prospects of there existing weapons that could inflict so much destruction. These actions changed the face of world relations not only then but forever.
The U.S. and the Soviet Union has been in a race to try and create an atomic bomb before the other could. The U.S. won the race but the Soviets succeeded in creating their own atomic bomb. The U.S. feared the spread of communism and also the idea that the Soviets would use their atomic weapons on the U.S. President Harry Truman and his advisors decided to drop the bombs for two main reasons. First they were dropped to make Japan surrender quickly instead of having a long, bloody war with them. Secondly the bombs were dropped to show the Soviets that the U.S. would use atomic weapons if necessary. Truman and others were not only focusing on the end of WWII but also on the future relations with the Soviet Union.
This is where the Cold War comes into the picture.