How the world's inventory of nuclear weapons grew — then shrunk again

The facts

• Today, there are approximately 15,000 nuclear warheads in military stockpiles around the world — and over 90% of them belong to the U.S. or Russia.
• But the U.S. and Russia have shrunk their respective arsenals by a combined 55,000 nuclear warheads since the late 1980s. About 6,000 of those have been removed from military stockpiles but are still awaiting dismantlement.
• Despite tense relations between the U.S. and Russia, the two countries have been successful in working together to reduce their stockpiles of warheads.
• But while the number of warheads has gone down, both nations are actively modernizing their weapons, making them harder to detect and more lethal than ever before. "The Pentagon envisions a new age in which nuclear weapons are back in a big way ... Russia has accelerated a dangerous game that the United States must match, even if the price tag soars above $1.2 trillion," the New York Times reports.
• The most recent nation to acquire nuclear weapons is the North Korean regime, which is estimated to have at least 15 warheads, though some experts say that figure could be as high as 80.
• As western nations steadily shrunk their arsenals after the signing of the Non-Proliferation Treaty in 1968, Pakistan and India engaged in a nuclear arms race, adding over a hundred warheads to their respective arsenals over 20 years.

Behind the numbers

• The 1968 treaty was a turning point in the Nuclear Age. Adopted by 190 states, the treaty is an agreement to stop the spread of nuclear weapons technology, while allowing the spread of nuclear power.
• "The NPT is the most successful public policy push of the 20th century," Jim Walsh of MIT's Security Studies Program told reporters at an event at Harvard's Nieman Foundation. "It has survived, and only gotten stronger, over time."

• But not every nation signed on. India, Pakistan and Israel opted out of the treaty, and recently, North Korea violated the terms of the treaty by developing nuclear warheads. Today, South Asia and North Korea are the two most unstable regions in terms of potential nuclear conflict.
• The countries that do have nuclear weapons have stabilized through "deterrence theory," which is the idea that states will not attack one another because their mutual destruction through nuclear war is assured.
• Israel has maintained its weapons to counter the potential of Iran and Saudi Arabia becoming nuclear states. Iran's nuclear weapons program has been temporarily halted by the Iran nuclear deal, which President Trump has threatened to pull the U.S. out of.