Alarms bells sounded this week in Europe after NATO jets scrambled to intercept an unprecedented Russian drone incursion in Poland. Now there is fresh unease on NATO’s eastern flank, as Russia and Belarus kick off major military drills to test the readiness of their armed forces.

NATO will launch a new deterrence initiative called "Eastern Sentry" in response to Russia's drone attack on Poland, the military alliance's secretary general Mark Rutte announced on Sept. 12.