Russia ratified a mutual defense pact with North Korea Wednesday, solidifying the military alliance between Moscow and Pyongyang. This comes as Ukrainian President Volodymyr Zelensky warned of a “new chapter of instability” after revealing his troops fought North Korean soldiers on the battlefield for the first time. The combat reportedly took place earlier this week in Russia’s Kursk region, though South Korea downplayed the encounter, labeling it an “incident” involving a small number of fighters. Ukraine says some 11,000 North Korean soldiers are now stationed in Kursk, where Ukraine launched a surprise counterinvasion in August.