U.S. President Donald Trump has consistently criticized allies for their lack of contributions to common security and defense efforts. A new article in Contemporary Security Policy shows he is partially right: The presence of U.S. military personnel abroad, while bolstering U.S global influence, also lowers the willingness of the host states’ citizens to fight for their own country.
U.S. President Donald Trump is clear in his demand that allies must contribute far more to common defense efforts. Even before becoming president, he claimed that allies “are not paying their fair share” and that they “must contribute toward their financial, political, and human costs … of our tremendous security burden”; and that if they do not, “the U.S. must be prepared to let these countries defend themselves.”
In short, the message is that defense burdens are unequally shared, and that allies unfairly free-ride on The United States’s military might. The United States’s military might, for its part, is unprecedented and unrivaled. The U.S. military budget exceeds 600 billion dollars, accounting for over one-third of world total military spending. The U.S. also has a vast, globally-spanning network of military bases, which no other country comes close to equaling.
These overseas military facilities have many noteworthy effects. One is that they significantly augment U.S. influence abroad and contribute to upholding U.S. hegemony – or Pax Americana. Another is that forward-deployed U.S. troops provide a “tripwire” that credibly conveys to any enemy of the ally that an attack on the latter will most likely draw in the United States. The tripwire function served by U.S. soldiers was brilliantly described by Thomas Schelling at the height of the Cold War; the same rationale still underlies much of U.S. base policies, including in states such as Japan, South Korea, and recently Poland as well. When U.S. troops are placed “in harm’s way,” deterrence is markedly strengthened. But so, too, is the ally’s knowledge that their patron cannot realistically abandon them. The ally’s scope for free-riding is therefore inevitably linked to the tripwire mechanism.
For U.S. allies, then, butter can to an extent be substituted for guns. This lies at the core of President Trump’s admonitions about allies’ purported free-riding: Their military spending usually make up only a meager share of total national income. On the other hand, it is quite common for allies of the United States to reciprocate by contributing in other ways; they often make other important policy concessions – such as providing access or basing rights, making financial contributions to the alliance, or, more generally, aligning their foreign policies closer to the United States.
This also means that it is not a straightforward exercise to measure whether allies “free-ride” on the United States. Still, the problem is more salient when burden-sharing and free-riding are conceived of as material – that is, as highly tangible – concepts (such as defense spending as a share of GDP). These are eminently measurable factors that the United States can influence quite directly. Things differ, however, when we consider the attitudes, norms, and values of the allies’ populace, such as the willingness to fight for their own country. The U.S. can certainly not have any direct power over the sentiments of people, which are exclusively intangible factors. This implies that, if the deployment of U.S. troops causes a lowering of citizens’ willingness to fight for their own country, the latter cannot as easily be compensated by policy concessions in other areas. Free-riding might therefore be more prevalent in its non-material version.
In our empirical analysis, which covers the period 1989–2014, we rely on global survey data that draw on the responses of over 200,000 people in about 100 countries. Our results show that citizens’ willingness to fight for their own country drops markedly if U.S. troops are stationed on their soil. Even when we control for a number of other relevant factors that can impact willingness to fight, U.S. overseas military bases remain a potent predictor. The forward-deployment of U.S. troops seems – as an unintended consequence – to contribute significantly to non-material free-riding by allies of the United States.
The results also indicate the existence of a tripwire- or free-riding threshold. One hundred U.S. troops, for example, are largely insufficient for purposes of creating a tripwire effect. A few hundred troops, however, may well be enough. And once U.S. troops numbers pass 500, and in particular 1000, it seems that the host state’s citizens become firmer still in their belief that their state’s defense has been credibly outsourced to the United States. These numbers approximate the size of a battalion – that is to say, an independently-functioning military unit. A battalion-sized U.S. force is a fully-working tripwire. But a battalion-sized U.S. force thereby also signals that the United States is providing for the defense of its ally – which essentially means that less is required by the ally itself.
The empirical evidence of non-material free-riding means that President Trump (and the many who share his opinion) is not necessarily in the wrong when he claims that allies free-ride. However, it is also true that U.S. alliances and forward-deployed troops are not acts of charity. They are, in fact, key ingredients of a long-standing grand strategy that stresses the centrality of a global presence; vital U.S. security and economic goals are served by the network of bases. Both the United States and its allies gain much and lose a bit from such relationships. For that reason alone, we can surely expect that the debates and bargaining about defense burdens and free-riding will continue for a long time.
Jo Jakobsen is a professor in political science at Norwegian University of Science and Technology (NTNU), Department of Sociology and Political Science. Tor G. Jakobsen is a professor in political science at NTNU Business School. They are authors of “Tripwires and free-riders: Do forward-deployed U.S. troops reduce the willingness of host-country citizens to fight for their country?”, Contemporary Security Policy, forthcoming.