Ukraine has seized more Russian territory in two weeks than Russia has seized in Ukraine all year. Reinforcements sent by Moscow failed to stop a Ukrainian surprise offensive in Russia’s Kursk region during its second week, creating a dilemma for the Kremlin – to further tap Russia’s invasion force in Ukraine by diverting more battalions to defend Russia, or to throw new conscripts into the war. Moscow has so far kept regular recruits into the armed forces on rotation at home, sending only contract soldiers to the bloody battlefields of Ukraine. But the Kursk offensive has changed that delicate political...