Country: South Africa
The government of South Africa began a nuclear-weapons program in the 1970s, and later acknowledged completing six nuclear warheads. But with the apartheid-era government under serious international pressure, it became the first country to voluntarily give up its nuclear program—a decision that was easier because the major security threat at the time was internal tension. Pretoria destroyed the bombs before even admitting they had existed.
During a military junta in the late 1970s, Brazil began work on a secret nuclear-weapons program parallel to its civilian power program, but São Paolo decided that nuclear weapons wouldn't help against an internal leftist threat, which was then considered the nation's biggest strategic challenge. Although Brazil has the technical capacity to produce weapons, it has signed several treaties pledging not to do so.
Like its neighbor Brazil, Argentina also developed a secret program in the 1970 and 1980s but stepped back from the brink because of more pressing domestic security issues. It has since signed the Nuclear Non-Proliferation Treaty and agreed to a bilateral inspection program with Brazil, committing not to develop nuclear weapons.
Despite ratifying the Nuclear Non-Proliferation Treaty in 1971, Taiwan maintained a secret program in the 1970s. After serious U.S. pressure and promises to sell Taiwan conventional weapons in exchange for giving up nuclear weapons, Taiwan agreed to abandon the program—although President Lee Teng-hui briefly suggested reviving it amid tensions with China in 1995.
Country: South Korea
Seoul began a weapons program in the 1970s, but by the time its government signed the Nuclear Non-Proliferation Treaty in 1975, it claimed to have abandoned it. The reasons for giving the program up are unclear, but the continued United States presence and nuclear umbrella there may have seemed to be sufficient for defense. Experts worried that a South Korean nuclear weapon could destabilize the region even more than a North Korean bomb, leading to a nuclear arms race with Japan or other regional rivals.
With high engineering capabilities, a missile capable of delivering a nuclear warhead, and large amounts of weapons-grade plutonium—produced as part of a civilian nuclear-power program—Japan has all the makings of a nuclear power, but Tokyo says it has no weapons. A Japanese weapon could destabilize the region, with World War II memories still lingering among its neighbors in Korea and China. And, at any rate, Japan is also covered by the U.S. nuclear umbrella.
Saddam Hussein began a nuclear-weapons program in the 1970s but suffered several setbacks, from an incident in 1981 when the Israeli Air Force bombed Iraq's Osirak reactor to Operation Desert Storm in 1991, which destroyed some facilities and forced Iraq to allow International Atomic Energy Agency inspections. Iraq's alleged arsenal of weapons of mass destruction was the Bush administration's justification for the 2003 Iraq War; no weapons were found after the invasion.
Sweden ran a nuclear program in the 1950s and 1960s, developing both nuclear power and weapons research. But because of the program's cost and the difficulty of developing a delivery system—it had no missiles of its own—it opted not to produce weapons and signed the Nuclear Non-Proliferation Treaty in 1968.
The regime of Muammar Kaddafi was considered a major proliferation threat for years. But in 2003, after the Iraq War, Great Britain brokered a deal whereby Tripoli agreed to dismantle its WMD program in return for improved relations with the West. The United States airlifted out tens of thousands of pounds of nuclear equipment in 2004.
The breakup of the Soviet Union instantly made Ukraine the owner of the world's third-largest nuclear arsenal, totaling about 5,000 weapons. The costs of maintaining it would have been immense, so Ukraine agreed to ship all of its warheads to Russia and to destroy the missiles they were mounted on, receiving hundreds of millions of American dollars in compensation.
Like Ukraine, Kazakhstan inherited a large arsenal when the Soviet Union collapsed, including some 1,400 nuclear warheads. But it couldn't maintain them. The country removed the last of its nuclear weapons in the spring of 2005, with missiles destroyed or sent to Russia; the United States also removed some uranium and plutonium.
Like those others, Belarus became a nuclear power when the Soviet Union dissolved, leaving it with 81 nuclear missiles. The arsenal was gradually dismantled and shipped to Russia, with the last nuclear materials leaving the country in 1996.
Countries: Syria, Egypt, Algeria
Status: They're not quite Not-Quite-Nuclear Nations
All three of these countries have toyed with nuclear-weapons programs. Egypt explored the possibility in order to counter Israel's own weapon, but Cairo has since called for a nuclear-weapons-free Middle East. In the 1980s, Algeria built a reactor able to produce enough plutonium for a bomb, but it then agreed to International Atomic Energy Agency oversight. Syria has also explored weapons development, and in September 2007, Israel bombed an alleged secret nuclear reactor in Syria. But the cost and difficulty of engineering the bomb probably put it out of reach for these countries.