Since last summer, Russian troops have been amassing on the Ukrainian border, and, in recent weeks, President Vladimir Putin warned that he intended a military takeover of Ukraine. This week, Russia began the war, with widespread attacks, including in the capital, Kyiv, aimed at crippling the Ukrainian military. The Ukrainian President, Volodymyr Zelensky, has called on civilians to enlist in the military to fight the invaders. The U.S. and nato are levying heavy sanctions against the Russians, but there are disagreements within the U.S. and among western allies about exactly how to proceed. Susan B. Glasser, a New Yorker staff writer, joins Dorothy Wickenden to discuss the war, and the choices faced by the Biden administration and nato.