“Robotyne has been liberated,” Ukraine’s deputy defence minister Hanna Maliar announced on August 28. Although the tiny village, which had a pre-war population of fewer than 500 people, may be of little importance in itself, it lies along a strategic road that leads to the Russian-occupied road and railway hub of Tokmak. From there, another road leads to the key city of Melitopol, which, prior to Russia’s illegal annexation of Crimea in 2014, was known to Ukrainians as the “gateway” to the peninsula. Last week’s victory was therefore an important advance for Ukraine. Just a few days earlier, however, fighters...