A global ban on the explosive testing of nuclear devices is the motivation behind the Comprehensive Test Ban Treaty. The treaty is viewed by its advocates as a means to avoid nuclear warfare and to lessen international tensions generally. Practically speaking, it is assumed that any nation with access to plutonium can fabricate, without explosive testing, a nuclear weapon like that dropped on Nagasaki by the United States in 1945. A ban on explosive testing deters an emerging nuclear state from developing more sophisticated weapons that employ plutonium fission or thermonuclear fusion or that are sufficiently compact to deliver on a missile. For countries with nuclear arms, a ban on testing does not render their weapon stockpiles ineffective. Rather, the ban is intended to deter them from modernizing weapon design. The test ban treaty is only one tool available to the international community to deter the proliferation of nuclear weapons. Export controls on fissile materials and nuclear technology, safeguards for weapon stockpiles, and regulations on plutonium disposal from nuclear power plants are also necessary.