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

© Ints Kalnins/Reuters NATO tanks and military vehicles are shown ahead of a live-fire exercise as part of the Iron Spear military drill in Latvia on Tuesday.

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.

What is Article 4?

Article 4 of the NATO charter says that member states “will consult together whenever, in the opinion of any of them, the territorial integrity, political independence or security” of another member is threatened.

It establishes a consultation mechanism among members, “to exchange views and information, and discuss issues prior to reaching agreement and taking action,” according to an explanation on the NATO website. “It also gives NATO an active role in preventive diplomacy by providing the means to help avoid military conflict.”

The primary forum for such discussions is the North Atlantic Council, the alliance’s political decision-making body.

Article 4 has been invoked seven times since NATO was established in 1949. Most recently, Latvia, Lithuania, Poland, Bulgaria, the Czech Republic, Estonia, Romania and Slovakia used it to hold meetings following Russia’s invasion of Ukraine.

Member states are not obligated to act if Article 4 is invoked, although deliberations could result in a decision to take joint NATO action.

Turkey, for example, invoked Article 4 in 2015 after at least 30 people were killed in a suicide bombing near its border with Syria.

At the time, the Turkish government said it wanted to inform its NATO allies about the measures it was taking in response to the attack. Following the meeting, the North Atlantic Council issued a statement saying that its members “strongly condemn the terrorist attacks against Turkey,” but it did not take further action.

What is Article 5?

Article 5 states that the parties to the NATO treaty “agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.”

It says that each member of NATO must take “such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.” It also authorizes the alliance to launch an armed response, but the wording is broad and leaves room for other types of action.

The collective defense clause was only invoked once, after the attacks in the United States on Sept. 11, 2001. NATO forces were subsequently deployed to Afghanistan.

Ukraine is not a NATO member but its open interest in joining the alliance has angered Russian President Vladimir Putin, who sees NATO’s eastward expansion as an existential threat.

When Russia invaded Ukraine in February, NATO activated its Response Force — a multinational conglomerate of 40,000 land, air, sea and special operations personnel — for the first time in its history. As part of the activation, NATO dispatched troops to countries bordering Russia and Ukraine, including Romania and Hungary, to augment the battle groups already stationed in the Baltic states and Poland.

In late January, before the invasion, U.S. Defense Secretary Lloyd Austin said: “Article 5 is clear on this point — an attack against one NATO member is an attack against us all. And as President Biden has said, the United States holds this as a sacred obligation and we will do right by that commitment.”

Emily Rauhala, Karoun Demirjian, Liz Goodwin, Karen DeYoung, Robyn Dixon and Paul Sonne contributed to this report.