NATOJoining NATO Binds Countries to Defend Each Other – but This Commitment Is Not Set in Stone

By Dan Reiter and Brian Greenhill

Published 20 June 2024

At the root of debates over policy toward alliances such as NATO is the assumption that NATO requires its members to step in and help with defense if another member of the alliance is attacked, but it is important to understand that, in reality, alliance agreements are more flexible than people think. In practice, it is possible for the U.S. and other Western countries to stay out of a conflict that involves a NATO country without having to break their alliance commitments.

The outcome of the upcoming U.S. presidential election is going to have major consequences for the relationship between the U.S. and its allies. While President Joe Biden is a firm believer in the value of the transatlantic alliance, Republican contender Donald Trump has for years railed against U.S. participation in the North Atlantic Treaty Organization, the military alliance commonly referred to as NATO.

In February 2024, for example, Trump said that if he were reelected president, he would tell Russia to do “whatever the hell they want” against NATO members that are “delinquent” in not having invested enough in their own military capabilities. Foreign policy commentators viewed that as an invitation for Russia to attack these NATO countries.

In September 2022, six months after Russia’s full-scale invasion, Ukraine applied to join NATO. Now, Ukraine’s potential membership is one of the top questions that representatives from NATO’s 32 member countries in North America and Europe will consider when they meet in Washington in July 2024.

At the root of debates over policy toward alliances such as NATO is the assumption that NATO requires its members to step in and help with defense if another member of the alliance is attacked.

As political scientists who study the role of international organizations like NATO, we think it is important to understand that, in reality, alliance agreements are more flexible than people think.

In practice, it is possible for the U.S. and other Western countries to stay out of a conflict that involves a NATO country without having to break their alliance commitments. The NATO treaty’s language contains loopholes that let member countries remain out of other members’ wars in certain situations.

What Does Article 5 Really Mean?
One key part of the NATO treaty that countries sign when they join the alliance is called Article 5. This says that an “armed attack” against one NATO member in Europe or North America “shall be considered an attack against them all.”

In the case of such an attack, NATO countries agree to assist the country that requires help, including through “the use of armed force, to restore and maintain the security of the North Atlantic area.”

But the treaty does not include a clear definition of a what an “armed attack” actually is.