NATO troop buildup to deter Russia is largest since Cold War

Russia’s 2014 annexation of Crimea radically changed the calculus between the West and Russia that has defined the last 25 years. NATO is now trying to reassure a nervous Eastern Europe and deter Moscow from new aggression. This level of tension hasn’t been felt in a generation. With the help of the Pulitzer Center on Crisis Reporting, Special Correspondent Nick Schifrin reports from Poland.