Three decades after the first cold war, experts believe the risk of nuclear war is as high as it has ever been. There are about 13,500 nuclear weapons in the stockpiles of at least nine countries, some hundreds of times more powerful than those that obliterated Hiroshima and Nagasaki at the end of World War Two. The use of even a small fraction of these weapons may be able to create a decade-long nuclear winter that could kill most people on Earth. Despite this, several superpowers are investing over a trillion dollars so as to make their nuclear arsenals more lethal. Many experts believe this will increase the risk of nuclear proliferation, nuclear terrorism, and accidental nuclear war – which has already almost occurred at least a dozen times.