After the A-bombings of Hiroshima and Nagasaki, on August 15, 1945 Japan surrendered unconditionally, bringing an end to World War II. In the postwar period, however, the East-West standoff known as Cold War began between the East, i.e., the socialist camp, led by the Soviet Union (now Russia) and the West, i.e., the capitalist camp, led by the United States. Under such circumstances, to prevent nuclear attacks from other countries, the major countries continuously conducted nuclear development and testing, in the attempt to acquire many powerful nuclear weapons.

After the collapse of the Soviet Union, the Cold War ended. However, even now the nations that possess nuclear weapons are unwilling to give them up, as they wish to protect themselves by means of these weapons. Moreover, some countries have newly acquired nuclear weapons, and other countries are suspected of possessing such arms.

Countries currently known to have nuclear weapons are the United States, Russia, the United Kingdom, France, China, India, Pakistan and North Korea. Israel is suspected of having nuclear weapons. It is said that throughout the world there are currently about 25,000 nuclear warheads that can be used as nuclear weapons. However, the exact figure is unknown.

In March 1954 the United States carried out a hydrogen bomb test on Bikini Atoll in the Marshall Islands, located in the Pacific Ocean. The radioactive fallout (small particles of coral reef containing highly radioactive materials) produced by the test fell on a Japanese fishing boat named Daigo Fukuryū Maru (Lucky Dragon No. 5), which was about 160 km from the test site. One of the crewmembers of the contaminated boat died in September of that year

The tragedy of the Daigo Fukuryū Maru evoked international concern regarding the horror of nuclear weapons, generating a groundswell in the movement against atomic and hydrogen bombs. In the following year, the first World Conference against A & H Bombs was convened.

In addition, some countries have concluded mutual agreements to ban nuclear testing and to reduce nuclear arsenals. Also, nuclear-weapon-free zone treaties have been signed among nations in certain regions.

In 1967, Japan decided not to make or possess nuclear weapons, and not to allow their entry into Japan (as stipulated in the Three Non-Nuclear Principles). As the only A-bombed nation in the world, it is important that Japan continue to appeal to the international community for the abolition of nuclear weapons.