Russia’s invasion of Ukraine is entering its fifth month, and there is no end in sight. The grueling conflict has shifted to the eastern provinces, where Russian progress in the Luhansk region has been described as “plodding.” Still, the Russians last week were on the verge of capturing the twin cities of Sievierodonetsk and Lysychansk. At the same time, the Ukrainians — increasingly well-equipped, courtesy of the West — talk boldly of taking back the southern city of Kherson, which the Russians overran early in the conflict.