Today's nuclear weapons are far more powerful than the first atomic weapons, developed during the 1940s by Robert Oppenheimer and the Manhattan Project.
Background: The Manhattan Project was responsible for the development of two types of atomic bombs — named Little Boy and Fat Man — that were detonated above the Japanese cities of Hiroshima and Nagasaki during World War II.
- They remain the only atomic bombs ever used in war.
- The bombs — first over Hiroshima and then over Nagasaki — killed tens of thousands of people when they were first detonated, and many more died in the days and weeks that followed due to radiation poisoning.
By the numbers: Nine countries are known to have nuclear warheads today.
- About 12,500 nuclear warheads total exist, according to an estimate from the Federation of American Scientists.
- The U.S. has about 5,244 nuclear warheads with about 1,536 of those retired, the FAS said in March.
- Russia is thought to have 5,889 nuclear warheads.
The most potent of those weapons are far stronger than Little Boy and Fat Man, and could cause devastation that would stretch for nearly 15 miles.
