Fmr. Amb. to Ukraine Marie Yovanovitch on the Ukraine War

Marie Yovanovitch served as U.S. ambassador to Ukraine after Moscow invaded Crimea. Removed from the post by President Trump, Yovanovitch later testified in his first impeachment trial about the withholding of U.S. aid from Ukraine. She joins Walter Isaacson to discuss how this war can end and why the West must not repeat the mistakes of Crimea.