On Feb. 25, a flurry of accurate Russian drone strikes knocked out dozens of Ukrainian vehicles along the main road to Sudzha, the town that is—or was—the main base for the 10,000-strong Ukrainian force occupying a significant, but quickly shrinking, salient in Kursk Oblast in western Russia. That was “the day you started worrying about Kursk,” wrote independent analyst Andrew Perpetua. Two weeks later, it seems the bulk of the Ukrainian force—Ukrainian army’s heaviest brigades—has evacuated Kursk and repositioned on the Ukrainian side of the border. “My friends managed to leave Kursk, avoiding encirclement,” one Ukrainian source claimed Monday. “It’s...