Joining NATO obliges countries to defend each other – but this commitment is not carved in stone

The end result of the upcoming US presidential election may have serious consequences for relations between the US and its allies. While President Joe Biden is strong believers When it comes to the worth of the transatlantic alliance, Republican candidate Donald Trump has for years complained about U.S. participation in the North Atlantic Treaty Organization, the military alliance commonly referred to as NATO.

For example, in February 2024, Trump said that if re-elected president, he would tell Russia to accomplish that “whatever the hell they want” against NATO members who’re “behind” because they’ve not invested sufficient resources in their very own military capabilities. Foreign policy commentators saw this as an invite for Russia to attack these NATO countries.

In September 2022, six months after Russia’s full-scale invasion, Ukraine applied for NATO membership. Now Ukraine’s potential membership is certainly one of the foremost questions asked by representatives 32 NATO member countries in North America and Europe will consider after they meet in Washington, D.C. in July 2024.

At the center of policy debates toward alliances equivalent to NATO is the belief that NATO requires its members to step in and help defend itself if one other alliance member is attacked.

How political scientists who study role of international organizations equivalent to NATO, we imagine it is essential to understand that in fact alliance agreements are more flexible than people think.

In practice, it is possible for the United States and other Western countries to stay out of a conflict involving a NATO country without having to violate their alliance commitments. NATO treaty language incorporates loopholes that allow member countries to stay out of other members’ wars in certain situations.

What does Article 5 really mean?

One of the important thing parts of the NATO treaty that countries sign after they join the alliance is called Article 5. This stipulates that an “armed attack” against one NATO member in Europe or North America “shall be considered an attack against them all.”

In the event of such an attack, NATO countries agree to provide assistance to the country in need of assistance, including through “the use of military force to restore and maintain the security of the North Atlantic area.”

However, the treaty does not provide a transparent definition of what an “armed attack” actually is.

This mattered in February 2020 when Türkiye asked for a NATO meeting and asked NATO to intervene forcefully in response to attacks by Russian and Syrian forces on its territory that resulted in the deaths of 33 Turkish soldiers through the Syrian civil war. NATO allies selected not to accomplish that defend Turkey with military force, arguing that the extent of violence against Turkey is not sufficient to call it an “armed attack”.

Other exceptions to the rule

Even if NATO members resolve that Article 5 should apply to a specific situation, each country can still resolve individually how to proceed. That is, while NATO does it have administrative staff working in Brusselsthere is no central NATO body that tells each country what it must do.

Instead, each country tells NATO what it wants – and doesn’t want – to do.

NATO members formally invoked Article 5 just once – after the attacks on the World Trade Center and the Pentagon near Washington on September 11, 2001.

At the time, 13 NATO countries sent fighter jets to help the US they patrol its skies from mid-October 2001 to mid-May 2002.

But most NATO allies decided not to send troops to Afghanistan to support the US in the fight against the Taliban. This lack of motion by some NATO allies was not seen as a breach of the treaty and did not generate much debate, and countries that selected not to join the fight were not sanctioned by or kicked out of the alliance.

The NATO treaty also provides for certain geographical exceptions. When Argentina went to war with Great Britain (a NATO member) over the Falklands in 1982, the United States and other NATO members were able to benefit from the undeniable fact that the alliance applies only to the North Atlantic region as a reason to steer clear of the conflict.

Would public opinion force the president to act?

Some political scientists say that voters will demand that their leaders take the country to war to defend an ally. This signifies that what really unites the members of the alliance is not the legal text of the international treaty itself, provided that no international court has the facility to implement the treatybut slightly the general public’s expectations of what it means to be an ally.

As part our research about how the American public thinks about international legal obligations, we decided to conduct an experiment to see whether presidents could use alliance-gap language to justify keeping the U.S. out of a war involving an ally.

In 2022 and 2023, we conducted two survey-based experiments in which we asked nearly 5,000 U.S. adults to consider a hypothetical scenario in which a U.S. ally is attacked by a robust neighbor.

Some respondents were told that the text of the alliance treaty would allow the U.S. government to avoid having to send troops to defend an ally in distress, but others were not told this information. Although the survey did not mention a selected alliance, we described the terms of the alliance in a way consistent with language used in treaties equivalent to NATO. We then asked respondents to present their views on sending US troops to defend an attacked ally.

Our results revealed a big difference between those that were told about the pliability of the alliance treaty and those that were not. While respondents in each groups were generally willing to defend an ally, their willingness to accomplish that decreased significantly after they were told that an alliance treaty did not necessarily require the U.S. to send troops.

This suggests that political leaders will, under certain circumstances, succeed in persuading a big segment of the population that it is okay to abandon an ally in need.

So when it comes to debates about U.S. policy towards alliance partners – and whether it should admit recent members like Ukraine – it is essential for each side to realize that alliance commitments are not as binding, either legally, as nor politically, as conventional wisdom suggests.