The situation could change quickly, however, if Moscow’s attack on Ukraine spilled into a NATO member nation and triggered a response based on the alliance’s Article 5 principle.
What is Article 5?
The principle aims to deter potential adversaries from attacking NATO members. Article 5 guarantees that the resources of the whole alliance can be used to protect any single member nation. This is crucial for many of the smaller countries who would be defenseless without their allies. Iceland, for example, has no standing army.
Since the US is the largest and most powerful NATO member, any state in the alliance is effectively under US protection.
According to the NATO website, Article 5 specifically lays out:
“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defense recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.”
Has Article 5 ever been invoked?
Article 5 has only been invoked once: After the September 11, 2001, terror attacks on the US.
But NATO’s Article 5 principle stretches beyond attacks on the homeland. The alliance has also taken collective defense measures on several occasions, including deploying Patriot missiles in 2012 on the Syrian-Turkish border and bolstering its forces in Estonia, Latvia, Lithuania and Poland following Russia’s annexation of Crimea in 2014.
NATO allies have also joined the US to fight in Afghanistan, Iraq and Syria.
How does Article 5 apply to Russia’s attack on Ukraine?
But many of Ukraine’s neighbors are NATO members, and if a Russian attack extended into one of those countries, Article 5 could trigger direct involvement from the US and other NATO members.
What constitutes an attack on a NATO member nation?
The Article 5 language specifies that an “armed attack” on a member nation is what triggers collective action.
But what constitutes an “armed attack” is up to NATO members, and Russia’s aggressive posture has already prompted concern about the country’s willingness to potentially tempt a NATO response.
“It could end up bleeding into Poland or Romania or into the Baltic states and cause damage that would shut down hospitals, and potentially, you’ve got American troops there. If American troops in a truck crash because the lights were out, you could get very close to Article 5,” Warner, the Senate Intelligence Committee chairman, told the outlet.
What are US officials currently saying about Article 5?
CNN’s Jeremy Herb contributed to this report.