Both Russia and Ukraine have been escalating their bloody conflict, now past the 1,000-day mark, seeking maximum advantage before Jan. 20, when President-elect Donald Trump will take office and probably bring a different U.S. policy toward the war. For Russia, escalation is about saving face — expelling Ukrainian forces from Russia’s Kursk region — and grabbing as much Ukrainian territory it can. For Ukraine, it’s a matter of surviving with its sovereignty and as much of its preinvasion territory as possible. Escalation might be a hard concept to grasp in a savage struggle that has led to an estimated 1...