Can history teach us what happens next? Almost eight decades after J. Robert Oppenheimer built the first atom bombs, the threat of nuclear annihilation seems real once again.
Russia threatens nuclear strike as Moscow hit
Bombastic: The nuclear threats come after Ukraine launched drones into the heart of Moscow. Glossary
Hiroshima - A Japanese city destroyed by an atomic bomb in World War II.
Nagasaki - A city in Japan that was hit by an atomic bomb during World War Two.
Vapourised - Turned into gas. It can apply to something which starts in either a solid or a liquid state.
Radiation sickness - Damage caused to the body after it receives a high dose of radiation in a short amount of time. It can be life-threatening.
Tactical nuclear weapons - Nuclear weapons that are meant to be used to make small gains on the battlefields, rather than to destroy whole cities.
Dmitry Medvedev - A Russian politician and former president and prime minister.
John F Kennedy - President of the US from 1961 to 1963, when he was shot dead in Dallas. He was the fourth American president to be assassinated; Abraham Lincoln was the first.
Nuclear stockpile - A country's collection of nuclear weapons.