Despite repeated warnings from the White House, Russia's invasion of Ukraine in February 2022 shocked the world. Why did Putin start the war--and why has it unfolded in previously unimaginable ways? Ukrainians have resisted a superior military; the West has united, while Russia grows increasingly isolated. Serhii Plokhy, a leading historian of Ukraine and the Cold War, offers a definitive account of this conflict, its origins, course, and the already apparent and possible future consequences.