In June last year, North Korean troops violated the border three times, prompting South Korea to fire warning shots. The incidents occurred when the Koreas were embroiled in Cold War-style campaigns like balloon launches and propaganda broadcasts, but they didn’t develop into a major source of tensions.

North Korea appears to have sent at least 3,000 more soldiers to Russia early this year, South Korea’s military said Thursday, demonstrating Pyongyang’s continued support for Moscow’s war on Ukraine as world leaders push for an end to the three-year conflict.