Peter Doran is an adjunct senior fellow at the Foundation for Defense of Democracies. John Hardie is deputy director of FDD’s Russia Program.

Russian President Vladimir Putin is testing Western resolve.

Russia’s unprecedented drone incursion into Poland marks the first time NATO aircraft ever had to shoot down hostile targets inside alliance airspace. This foreshadows the dangers to come if the White House and Europe don’t respond in a muscular manner. And that means strengthening NATO air defenses, approving Kyiv’s use of U.S. missiles to target inside Russia, tightening oil sanctions and more.

This incursion wasn’t a lone malfunctioning drone gone astray. According to Polish authorities, some 19 unmanned aerial vehicles crossed into Polish airspace during a larger Russian drone and missile barrage against Ukraine. Moreover, the number of drones that entered Poland — along with their reported flight paths and the extra fuel bladders extending their range — suggests Western officials are correct to contend the incident was intentional. Fortunately, it appears that most or all the projectiles were “Gerbera” drones without warheads, typically used as decoys.

But as Warsaw’s residents awoke to the booms of Polish and Dutch fighter jets and other aircraft scrambling to intercept the Russian drones, Polish Prime Minister Donald Tusk words were clear: “A line has been crossed.” And in response to a request from Warsaw, allied officials quickly convened for consultations under Article 4 of the North Atlantic Treaty.

NATO Secretary General Mark Rutte followed with a carefully calibrated message to Putin, declaring member countries would “defend every inch of Allied territory.” Ambassador Matthew Whitaker, the U.S. envoy to NATO, echoed that statement. Now, U.S. President Donald Trump would be wise to reiterate it, both publicly and privately, to Putin.

Trump knows that Warsaw is a serious ally. His meeting with Polish President Karol Nawrocki last week highlighted this fact. We’re not talking about some distant country Washington knows little about — this is a key U.S. ally that shares core values and mutual defenses against Russian aggression, with 7,500 American soldiers stationed there.

And this time, words alone won’t be enough. Whatever Russia’s intentions behind the drone incursion may be, Moscow will be watching to see how the West responds. Weakness and hesitation will only risk emboldening Putin. To ensure he learns the right lesson, the alliance needs to demonstrate strength.

First and foremost, NATO needs to bolster its air defenses, quickly fielding cost-effective means of countering mass drone attacks like those Russia routinely launches against Ukraine. The alliance has been far too slow in learning from Ukraine’s experience in this area, and relying on expensive missiles to shoot down large numbers of relatively cheap drones would be unsustainable during a hot war.

The drone incursion into Poland must serve as a wake-up call.

Crucially, NATO — or, more likely, a coalition of select allies — should consider extending its air defense air umbrella into western Ukraine to help Kyiv’s forces shoot down Russian drones and missiles. This move might draw on the plans of the British- and French-led “coalition of the willing,” which has promised postwar security guarantees for Ukraine. Though complex to execute, this would demonstrate seriousness to the Kremlin.

America’s role will be key here. And during its ongoing force posture review, the Pentagon should think twice before reducing U.S. military presence in Europe — its top trading partner.

U.S. defense officials are right to prioritize the threat from China, but as Europe undertakes a years-long process of rearmament, Washington must take care not to leave capability gaps that risk inviting aggression. Instead, it should signal unwavering commitment by maintaining a robust forward presence.

The incident in Poland also provides good reason to revisit the question of terminating the outdated NATO-Russia Founding Act of 1997, clearing the way for permanent rather than rotational deployments in eastern flank countries.

Additionally, the Trump administration should drop its prohibition on Ukraine using U.S. missiles and targeting data for strikes inside Russia. In concert, it should provide Kyiv with as many long-range missiles as possible, including ones that can reach key military-industrial sites deep inside Russia, such as the plants producing Gerbera and Shahed-type drones.

Finally, Washington and European allies should apply overwhelming economic power to deny Putin the money he needs to wage war in the first place. This should include new secondary sanctions targeting Russia’s oil export revenue, as they would likely have greater impact than tariffs — which have so far failed to halt purchases of Russian oil and face competing objectives in trade talks.

This week’s incursion is a reminder that deterrence must be continually maintained. Thankfully, this provocation resulted in no loss of life, but the next one could be deadly.