World War II[r]: (1931–1945) global war killing 53 million people, with the "Allies" (UK, US, Soviet Union) eventually halting aggressive expansion by the "Axis" (Nazi Germany and Japan). [e]
TNT equivalent[r]: A unit of energy commonly used to quantify the energy released (or "yielded") in explosions. [e]
Hiroshima (city)[r]: Japanese city; capital of Hiroshima prefecture in the Chugoku region of Honshu island. [e]
Nagasaki (city)[r]: Capital city of Nagasaki prefecture on the Japanese island of Kyushu. [e]
Harry S. Truman[r]: (1884-1972) President of the U.S. from 1945 to 1953. [e]
Albert Einstein[r]: 20th-century physicist who formulated the theories of relativity. [e]
Plutonium[r]: Mainly man-made radioactive element (Z = 94); its 239 isotope is fissionable and used in nuclear weapons; the 240 isotope is used in some nuclear power reactors [e]
Uranium[r]: A silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. [e]