Ukraine enjoyed a triumphant autumn. General Syrsky’s lightning advance through Kharkiv prompted Putin to appoint a new commander and conscript 300,000 soldiers. So precarious was Russia’s position in October that its generals began discussing nuclear options. The Commander-in-Chief of the Armed Forces of Ukraine, Major-General Valeriy Zaluzhny. Alamy In November, Ukrainian forces walked into Kherson city. “This is the beginning of the end of the war,” declared Zelensky as he strolled through the newly liberated city. “We are step by step coming to all the temporarily occupied territories.” But neither General Zaluzhny nor General Syrsky sounds triumphant. One reason is...