SEOUL, South Korea — For the second time in less than a month, North Korea has fired a ballistic missile over Japan, days after the international community further tightened its sanctions over its banned weapons and nuclear program. Here’s how the program got to where it is: Late 1970s: North Korea starts working on a version of the Soviet Scud-B (range 300 kilometers or 186 miles). Test-fired in 1984 1987-92: Begins developing variant of Scud-C (500 km), […]