SEOUL, South Korea (AP) — Following U.S. warnings to North Korea of a “massive military response,” South Korea fired missiles into the sea to simulate an attack on the North’s main nuclear test site on Monday, a day after North Korea detonated its largest-ever nuclear test explosion. South Korea’s Defense Ministry also said Monday that North Korea appeared to be planning a future missile launch, possibly of an ICBM, to show off its claimed ability to target the United States with nuclear weapons, though it was unclear when this might happen. The heated words from the United States and the...