Why is NATO’s Article 5 being discussed after blasts in Poland?

Two people were killed in explosions Tuesday in the Polish town of Przewodow on the border with Ukraine, according to a Polish official. The incident came amid a day of heavy Russian strikes on Ukrainian territory, but it was unclear where the reported strike in Poland came from, or whether it was deliberate.

Because Poland is a member of the North Atlantic Treaty Organization, a 30-member military alliance, a strike on the country could mark a pivotal moment in the Russia-Ukraine war — depending on what actually happened.

Despite the fact that authorities are still investigating the source and cause of the explosions, news of the incident quickly led to speculation about NATO’s Article 5, which states that “an armed attack against one or more of [the members] in Europe or North America shall be considered an attack against them all” and that force can be used in response.

While clear-cut evidence of a deliberate Russian attack on Poland could theoretically lead a country to invoke Article 5, Polish authorities have yet to provide such details, and U.S. and European officials stressed Tuesday evening that they are still collecting information and coordinating among allies.

A more likely — but not certain — outcome is that Poland could invoke Article 4 of NATO’s founding treaty, which allows members to bring any issue of concern, especially related to security, for discussion at the North Atlantic Council, the alliance’s political decision-making body. This would give members the chance to come together to discuss the next steps.

Polish Prime Minister Mateusz Morawiecki on Tuesday called an emergency meeting of the country’s national defense and security council. In a statement, Russia’s Defense Ministry said it did not strike any targets in or near Poland.

Oana Lungescu, a spokesperson for NATO Secretary General Jens Stoltenberg, said he would chair a meeting of alliance ambassadors Wednesday morning in Brussels “to discuss this tragic incident.”

The North Atlantic Council of ambassadors from the 30 member states normally meets on Wednesdays; Stoltenberg has set the session as an emergency agenda item.