Russian drones that flew into Poland last week were almost certainly not there by accident. Around 19 Russian drones entered Polish airspace overnight on 9 and 10 September, some coming through Belarus. This was the first engagement between NATO aircraft and Russian drones over allied territory. In response to the incursion, NATO has launched Operation Eastern Sentry, deploying more air-defence equipment, including fighter jets and a frigate, to its eastern flank. If Russia can get away with such violations, it pushes out the threshold of the grey-zone spectrum of provocations less than war.