Nuclear history began in the early 20th century with discoveries in atomic physics, notably by scientists like Marie Curie and Albert Einstein. The development of nuclear fission in the 1930s led to the creation of nuclear weapons during World War II, culminating in the bombings of Hiroshima and Nagasaki in 1945. The post-war era saw the Cold War, where the United States and the Soviet Union engaged in an arms race, leading to the proliferation of nuclear weapons. International treaties, such as the Nuclear Non-Proliferation Treaty (1968), aimed to prevent the spread of nuclear arms and promote peaceful uses of nuclear energy.