By William Arkin January 29, 2020 Ten days before Donald J. Trump was elected president in 2016, the United States nuked Iran. The occasion: a nuclear war exercise held every year in late October. In the war game, after Iran sank an American aircraft carrier and employed chemical weapons against a Marine Corps force, the Middle East commander requested a nuclear strike, and a pair of B-2 stealth bombers, each loaded with a single nuclear bomb, stood by while the president deliberated. “Testing our forces through a range of challenging scenarios validates the safety, security, effectiveness and readiness of the strategic deterrent,” Adm. Cecil D. Haney, then the commander of U.S. Strategic Command, said as the exercise got underway. According to a government contractor who helped write the complex scenario leading up to the decision to use nuclear weapons, Global Thunder 17 (as the exercise was called because it took...