How do military alliances shape support for military interventions globally? Evidence from a cross-national experiment

In the newly published peer-reviewed article “Allied Commitments and Public Support for Military Interventions: A Cross-National Experiment,” Marek Vranka from the ICSJ FSV UK, together with his colleagues Michal Smetana and Ondřej Rosendorf, analyze whether formal alliance treaties boost public willingness to support military interventions and whether this effect holds beyond the Western world.

The study, published in Research & Politics and available via open access, employed an experiment with short fictional scenarios. The researchers randomly assigned participants to one of several versions of a scenario describing armed aggression against an unnamed country. In each version, the researchers randomly manipulated four pieces of information:

• whether the victim had a military alliance with the participant's country,
• whether the victim was a democracy,
• whether the participant's country had high security and economic stakes in the conflict,
• and whether the intervention would be costly. 

After reading the scenario, participants indicated their support for sending their country's military to stop the invasion.

Using this pre-registered survey experiment across nationally representative samples in six countries (the United States, the United Kingdom, Russia, China, India, and Brazil), their study provides first experimental evidence that formal alliance commitments shape public support for military interventions globally. The effect is comparatively weaker in non-Western, non-NATO countries. In other words, citizens in NATO member states are more strongly influenced by alliance obligations when forming attitudes on military interventions than citizens in non-Western countries.

“One possible explanation may be the fact that people in China or India are, on average, significantly more willing to support military intervention—regardless of whether a military alliance exists between their country and the attacked state,” adds Marek Vranka.

It is also interesting to compare the current findings with results from earlier studies conducted on participants from the United States. Although alliances still increase support for military assistance to an attacked country, their effect used to be much stronger in the past, particularly among Republican voters. This shift may reflect recent changes in the attitudes of this segment of the U.S. population toward NATO.

The study was conducted as part of the MICROCODE research project, supported by an ERC grant under the leadership of Michal Smetana.

This article was first published on the Peace Research Center Prague website.