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What Drives Public Support for Humanitarian Interventions?

What Drives Public Support for Humanitarian Interventions?

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This analysis summarizes and reflects on the following research: Kreps, S., & Maxey, S. (2018). Mechanisms of morality: Sources of support for humanitarian intervention. Journal of Conflict Resolution, 62(8), 1814-1842.

Talking Points

  • In the United States, military interventions conducted for humanitarian objectives receive significantly higher public support than interventions serving security interests.
  • The most important factor behind public support for humanitarian interventions was the view that the United States had a moral obligation to protect civilians.
  • Republicans exhibited high levels of support for the use of force across the board, regardless of type of intervention, whereas Democrats and Independents exhibited lower levels of support for the use of force overall with an increase in support in the case of humanitarian intervention.
  • Independents consistently showed the least support for military intervention.


Humanitarian interventions have become a common aspect of United States foreign policy, especially over the last several decades. Since the 1990s, over half of U.S.-led interventions have purportedly been motivated by humanitarian objectives, including Somalia in 1993, Bosnia in 1995, and Libya in 2011. As with all military action, however, the human and economic costs of war must be justified to the public whose support, or lack thereof, can influence the trajectory of U.S. involvement. Public opinion plays a particularly important role in humanitarian interventions because “rather than responding to security threats, these operations rely on the public’s belief that military action to protect foreign civilians is in the interest of the United States and worth the potential cost.” The important role public opinion plays in determining the involvement, methods, and longevity of a particular intervention thus becomes a significant topic of study for academics, as well as for political decision-makers or practitioners working to conduct or avoid these interventions. The respective stakeholders are eager to understand what drives public opinion on this matter.

Humanitarian intervention “the deployment of military force across borders, without the consent fo the target state, with the predominant purpose of preventing or ending the widespread suffering or death of foreign civilians.”

In this article, the authors use a series of survey experiments to identify the main drivers behind U.S. public support for humanitarian interventions. They structure their surveys to consider three potential sources of an individual’s attitude towards humanitarian interventions, including views about costs, strategic consequences, and moral obligation. The authors then try to narrow in on the specific “mechanisms of morality,” derived from the most common drivers of the respondent’s moral convictions about intervention, and also incorporate survey questions on political partisanship and various other related variables.

The first survey examined differences in support between two hypothetical military intervention scenarios: one focused on protecting civilians and the other focused on more defined security objectives. The former involved a foreign leader invading another country to restrain the government from harming civilians, and the latter involved a foreign leader invading another country to gain power. The next survey involved the same situations but replaced “foreign leader” with “U.S. President” to see if attitudes would change depending on where the invading forces originated. The survey respondents were also asked questions about the motivation behind their support/lack of support, including questions around morality, costs, and strategic consequences. Morality was gauged by asking whether the U.S. had a “moral obligation to intervene.” Costs were gauged by asking questions regarding the likelihood of U.S. casualties, the financial costs of the operation, burden-sharing and multilateral authorization, and military strategy. Finally, strategic consequences were gauged by asking the respondents about the potential consequences if the U.S. didn’t intervene, including “creating a breeding ground for terrorists” and “generating reputational costs.” A different survey was used to separate morality into five different components to identify which aspect of morality was most influential in a respondent’s support for humanitarian intervention: harm/care (responding to harm done to vulnerable civilians); fairness/reciprocity (the desire to hold perpetrators of violence against civilians accountable); authority/respect (upholding international law regarding the treatment of civilians); purity/sanctity (upholding the standards of common decency accepted by civilized countries); or in-group/loyalty (American exceptionalism: the U.S. doesn’t turn a blind eye to atrocities).

The survey findings showed that humanitarian objectives attract high levels of public support. Just over half of respondents supported a military intervention with more defined security objectives, while 80% of respondents supported a humanitarian intervention scenario. “Moral obligation” was the most significant factor behind over half of the respondents’ support, easily outpacing factors of cost and strategic consequences. In the subsequent survey separating morality into five main concerns, fear of harm being done to civilians was the most significant factor in an individual’s support—individuals were less concerned about whether intervening would allow foreign leaders to get away with human rights abuses, create a dangerous international environment, contradict U.S. values, or permit violations of “civilized” behavior. Interestingly, the belief in the United States’ moral obligation to protect civilians was common among major political parties, but partisan differences began to emerge when respondents were asked about support for other types of military intervention. Republicans exhibited high levels of support for the use of force across the board, regardless of the type/reasons given for the intervention, whereas Democrats and Independents exhibited lower levels of support for the overall use of force with an increase in support in the case of humanitarian intervention. Additionally, Independents consistently showed the least support for intervention, while Democrats’ support for both interventions was in the middle, with a sharp spike in favor for humanitarian interventions. 

Contemporary Relevance

This research advances understanding on why and under what circumstances people are most likely to support so-called humanitarian interventions, which, due to the nature of military actions involved, should be considered wars. These findings also provide an opportunity to reflect on past wars supposedly conducted for humanitarian reasons, while making us more cautious about the humanitarian buzzwords that are likely to be used in the future when leaders seek public support for military action. By identifying that most Americans are supportive of humanitarian interventions, and that this support stems mostly from a sense of moral obligation to protect civilians, this research reinforces what political leaders already largely know: that providing a humanitarian justification provides them with a solid path for garnering public support for military action, as long as they are able to sell the notion that a “good war” is necessary to protect human life from “evil.” An ongoing question is: can humanism be exported through force?

Looking back on past U.S. interventions, the public is often (initially or through a conflict’s evolution) unaware of the true motives behind military action until long after U.S. involvement ends. During the 2011 NATO operation in Libya, the Obama administration clearly stated that the U.S. role was to protect the Libyan people and establish a no-fly zone, and that broadening the scope of the operation to include regime change would be a mistake. We now know, however, many events that transpired in Libya—including regime change—were in direct contrast to the administration’s original justification for military intervention. Although the argument that NATO’s intervention prevented a massacre in Benghazi is made, the overall humanitarian achievements of the intervention are mixed: a no-fly zone was never imposed, rebel forces were permitted and supported in their rise to power that posed further threat to civilian lives, lengthened the civil war, and contributed to the rise of stronger militant groups like ISIS—bringing along more civilian casualties. Most importantly, military interventions was once again placed over viable nonviolent alternatives that presented themselves at many points. 

Practical Implications

The findings from this research could be used in two ways. First, political leaders could use the findings of this study to inform how they frame military interventions in order to garner the most public support—a use that certainly is not in the interest of those of us who advocate for nonviolent responses to any form of conflict. Due to the public’s strong support for military action when conducted for humanitarian reasons, political leaders can potentially manipulate the public’s sense of morality to fit their foreign policy agendas by capitalizing on a humanitarian crisis to gain backing for military interventions conceived with more strategic geopolitical or economic goals in mind. Second, by recognizing this primary application of the research, active citizens can be doubly vigilant about keeping their governments in check by critically attending to the justifications provided for military interventions and engaging in advocacy for viable nonviolent alternatives. Peace- and justice-oriented institutions such as the Institute for Policy Studies, the Center for International Policy, and our own War Prevention Initiative provide strong analysis that is grounded not in idealism but rather in a rigorous examination of the context, the unintended effects of military action, and the myriad preferable alternatives.

This research serves as an important reminder that political leaders need the public’s support to undertake or sustain a military intervention—and that therefore the public can also choose to withhold this support if they realize they are being manipulated to facilitate a military intervention. 

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