Poland officially invoked NATO’s Article 4. But what does this actually mean?

Design by Alexandra Kolaya

On Sept. 9, Poland’s air force shot down several Russian drones flying in Polish airspace. Over the course of seven hours, Poland’s military reported 19 separate airspace violations, the most serious since Russia’s full-scale invasion of Ukraine began in 2022. 

The violations were particularly concerning because some drones appeared to originate from Belarus, a close ally of Moscow and host to Russian military forces. Belarusian officials dismissed the reports as “propaganda” and Russia declined to comment.

In an official statement, NATO Secretary General Mark Rutte condemned the attack. “Whether it was intentionally or not, it is absolutely reckless. It is absolutely dangerous. But as I said, the full assessment is ongoing.”

NATO’s Article 4 allows any member to request urgent consultations if it believes its security is under threat. While invoking Article 4 does not trigger military action, it forces allies to formally meet and coordinate a collective response. By invoking it, Poland ensured that the incident would be treated not just as a national concern, but as a matter for the entire alliance.

This is not to be confused with Article 5, NATO’s most well-known clause, which commits members to treat an armed attack on one as an attack on all. It has only been invoked once, after the terrorist attacks on Sept. 11 in the US.

European Union foreign policy chief Kaja Kallas emphasized the seriousness of the violations. “Last night in Poland we saw the most serious European airspace violation by Russia since the war began, and indications suggest it was intentional, not accidental.”

Polish Foreign Minister Radoslaw Sikorski echoed that point in a video posted on social media before visiting Kiev. “On the night that 19 Russian drones crossed into Poland, 400 plus 40 missiles crossed into Ukraine. These were not mistakes,” he said. Poland’s framing of the incident as deliberate is meant to rally NATO toward stronger deterrence measures.

Prime Minister Donald Tusk was similarly blunt. “We would also wish that the drone attack on Poland was a mistake. But it wasn’t. And we know it.”

On Sept. 12, Rutte announced the launch of Eastern Sentry, a project aimed at strengthening NATO’s presence along its eastern flank. The initiative underscores the alliance’s commitment to deterring future airspace violations and to reassuring frontline allies such as Poland and the Baltic states.

Rutte ended the conference with a stark warning to Moscow. “My message is clear: stop the war in Ukraine. Stop the escalating war, which [Putin] is now basically mounting on innocent civilians and civilian infrastructure. Stop violating Allied airspace. And know that we stand ready, that we are vigilant, and that we will defend every inch of NATO territory.”