Drone incursions into NATO airspace raise question over need for overlapping Articles

On September 19, for only the ninth time in NATO’s history—and the second time in less than two weeks—Article 4 of the North Atlantic Treaty, the NATO alliance’s founding document, was invoked. While Poland triggered the clause two weeks earlier, the most recent invocation came from Estonia, both in response to what were seen as deliberate incursions by Russian aircraft into their airspace.

For Poland, the violation involved 19 Russian drones entering and lingering in Polish territory. Some were later shot down by Polish fighter jets with support from the Netherlands, a fellow NATO ally. Estonia’s case involved three Russian MiG-31 fighters that crossed into its airspace over the Baltic Sea and remained for more than 10 minutes.

An article published by the World Politics Review recalls the 2019 incident with Türkiye, when it shot down a Russian jet that had strayed into its airspace for less than 30 seconds. Against the backdrop of Russia’s ongoing war in Ukraine, the author argues that Estonia is justified in viewing the much longer incursion as highly provocative.

Other NATO members have also faced similar incidents in recent weeks. Russian drones breached Romanian airspace last week, and this week yet-unidentified drones twice forced the shutdown of airports in Denmark—whose government is now weighing whether to invoke Article 4 as well.

Why would Moscow risk such provocations while already engaged in a major war? Analysts suggest a straightforward answer: because it can. So long as no actual military strike is carried out, Russian officials know these incursions can aggravate NATO allies, perhaps distract them, without direct consequences. They may also be probing NATO’s resolve—and specifically testing whether the United States will stand firmly by its allies.

If that is the intent, Russia’s answer is clear. Mike Waltz, the newly appointed US ambassador to the United Nations and former national security adviser under Donald Trump, stated this week that the administration would “defend every inch” of NATO territory, echoing the US president's earlier pledge.

These incidents, however, highlight deeper questions: How serious are Russia’s actions, and what does invoking Article 4 truly mean?

Similar sentiment from different eras

Article 4 is often described as the “neglected younger sibling” of Article 5, NATO’s well-known mutual defence clause. Article 5 pledges that an attack on any member will be treated as an attack on all, committing each ally to respond, though with flexibility in how. Article 5 has been invoked only once: after al-Qaida’s September 11, 2001 attacks on the United States.

According to the article, Article 4, by contrast, carries weaker language: “The Parties will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security of any of the Parties is threatened.”

Poland and Estonia used it to convene the North Atlantic Council, NATO’s decision-making body, to determine how to respond. Following Poland’s request, NATO launched Operation Eastern Sentry on September 12, sending air-defence and monitoring assets to Poland and other eastern flank allies, along with fighter jets to patrol Polish skies.

In practice, the outcomes of recent Article 4 invocations mirror NATO’s only Article 5 action: deploying extra resources to monitor and protect an ally’s airspace.

This raises the question of whether NATO truly needs both provisions. If Article 4 can yield the same response as Article 5, perhaps it alone suffices.

The article points out that some argue that Article 5 reflects the geopolitics of its era: the 1940s and 1950s, when mutual defence treaties proliferated.

At the time, the US signed numerous such agreements, while the Soviet Union mirrored the practice in its Warsaw Pact with Eastern European satellites. These treaties were designed to deter, especially amid fears of nuclear war and a potential World War III.

Over time, however, such treaties have shifted. Data from the Alliance Treaty Obligation and Provision project shows a move toward “consultative” agreements. NATO’s Article 4 fits this model, and indeed, all nine invocations of the clause have occurred in the 21st century.

"In other words, in today’s world, the appropriate response by allies to a security threat is to consult—what Article 4 explicitly calls for and what Article 5, the only time it was invoked, effectively resulted in. But that’s not to diminish the significance of invoking Article 4, as Poland and Estonia have done. To the contrary, in the contemporary security landscape, it is the functional equivalent of invoking Article 5. And that makes it a big deal," the article concludes.

By Nazrin Sadigova