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 on Friday launched an operation named Eastern Sentry to bolster the defence of Europe's eastern flank in response to Russian drone incursions into Polish airspace earlier this week, Secretary-General Mark Rutte said.

The U.S.-led military alliance said it would bolster defenses along its eastern flank after the incursion, the first of its kind since the Ukraine war began; Russia denied targeting Poland.

Nato has deployed 40,000 soldiers to Poland's eastern border as Europe braces itself for major joint military exercises between Russia and Belarus. The shift of troops comes just days after at least 19 Russian drones infiltrated Polish airspace,

More than 20,000 Poles signed up for voluntary military training in the first seven months of 2025 - in line with record levels last year.

The incident represented the most serious spillover of the war in Ukraine for NATO, as its aircraft engaged the drones that it said came from Russia.

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.

European leaders on Thursday expressed alarm over growing Russian hostility threatening their countries as Moscow's forces pursue their invasion of Ukraine -- concerns exacerbated by events of the previous day when multiple Russian drones struck Polish soil.

Some of Kyiv's allies in NATO are discussing sending troops to Ukraine as part of security guarantees after Russia's war ends.