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

This mattered in February 2020, when Turkey asked for a NATO meeting and requested that NATO intervene with military force in response to Russian and Syrian forces’ attacks on its territory, which had killed 33 Turkish soldiers, during the Syrian civil war. NATO allies chose not to defend Turkey with military force, arguing that the level of violence against Turkey wasn’t enough to call it an “armed attack.”

Other Exceptions to the Rule
Even when NATO members decide that Article 5 should apply to a specific situation, each country can still individually decide how to act. That is, while NATO does have administrative staff based in Brussels, there is no central NATO authority that tells each country what it must do.

Instead, each country tells NATO what it is – and is not – willing to do.

NATO members have only formally invoked Article 5 once – following the Sept. 11, 2001, attacks on the World Trade Center and the Pentagon outside of Washington.

At that time, 13 NATO countries sent fighter aircraft to help the U.S. patrol its skies from mid-October 2001 to mid-May 2002.

But most NATO allies chose not to send troops to Afghanistan to support the U.S. in its fight against the Taliban. This lack of action on the part of some NATO allies was not seen as breaking the treaty and didn’t prompt a major debate – and the countries that chose not to join the fight were not sanctioned by or ejected from the alliance.

The NATO treaty also provides some exceptions based on geography. When Argentina went to war with the United Kingdom (a NATO member) over the Falkland Islands in 1982, the U.S. and other NATO members were able to use the fact that the alliance only applies to the North Atlantic region as a reason to stay out of the conflict.

Would Public Opinion Force the President’s Hand?
Some political scientists argue that voters will demand their leaders take the country to war to defend an ally. This implies that what really binds the members of an alliance together is not the legal text of an international treaty itself, given that no international court is empowered to enforce the treaty, but rather the public’s expectations of what it means to be an ally.

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

In 2022 and 2023, we conducted a pair of survey-based experiments that involved asking nearly 5,000 American adults to consider a hypothetical scenario in which a U.S. ally comes under attack from a powerful neighbor.

Some of the respondents were told that the text of the alliance treaty would allow the U.S. government to avoid having to send troops to defend the embattled ally, while others were not told that information. Though the survey did not mention a specific alliance, we described the terms of the alliance in a way that matches the language used in treaties like NATO’s. We then asked the respondents to tell us their views on sending U.S. troops to defend the ally under attack.

Our results revealed a big difference between the people who were told about the flexibility in the alliance treaty and those who were not. While respondents from both groups were generally inclined to come to the defense of an ally, their willingness to do so was significantly lower when they were told that the alliance treaty did not necessarily require the U.S. to send troops.

This suggests that political leaders can, under certain circumstances, manage to convince a large segment of the public that it’s OK to abandon an ally in a time of need.

So, when it comes to debates about U.S. policy toward its alliance partners – and whether it should admit new members like Ukraine – it is important for both sides to appreciate that alliance commitments are not quite as binding, either legally or politically, as the conventional wisdom suggests.

Dan Reiter is Professor of Political Science, Emory University. Brian Greenhill is Associate Professor of Political Science, University at Albany, State University of New York. This article is published courtesy of The Conversation.