Russia went all in last week, sending troops across the border with Ukraine and raining shells on the country. Experts are saying Putin’s brash invasion of his neighbor is shifting the world order in significant ways. In the face of this aggression, how should NATO respond? Can history serve as a guide? Guest: Fred Kaplan, Slate’s War Stories correspondent. If you enjoy this show, please consider signing up for Slate Plus. Slate Plus members get benefits like zero ads on any Slate podcast, bonus episodes of shows like Slow Burn and Dear Prudence—and you’ll be supporting the work we do here on What Next. Sign up now at slate.com/whatnextplus to help support our work. Learn more about your ad choices. Visit megaphone.fm/adchoices