KYIV, UKRAINE — For weeks, Ukrainian troops braced for an unfamiliar enemy: North Korean soldiers sent to bolster Moscow’s forces after Ukraine launched a lightning-fast incursion and seized territory in Russia’s Kursk region over the summer. Their arrival marked a new and alarming phase in the war. And while initially inexperienced on the battlefield, North Korean troops have adapted quickly — a development that could have far-reaching consequences as they gain combat knowledge in the war against Ukraine. Unlike the Russian troops Ukraine has been battling for nearly three years, Kyiv’s forces were uncertain about what to expect from this