The rapid-fire overthrow of the theocratic Taliban regime in Afghanistan (2001) and Saddam Hussein’s Baathist dictatorship in Iraq (2003) by the United States—and the disastrous aftermaths of those and other recent interventions (such as the ouster of Libya’s Muammar el-Qaddafi in 2011)— has sparked popular and scholarly interest in the causes and consequences of foreign-imposed regime change (FIRC). One of the enduring puzzles about FIRCs is that, as highlighted in Melissa Willard-Foster’s terrific book Toppling Foreign Governments, three-quarters of them are carried out by great powers against minor powers in situations of extreme power asymmetry. “Though this asymmetry of power makes an imposed change feasible,” writes Willard-Foster, a political scientist at the University of Vermont, “it should also make that change unnecessary” because “militarily weak leaders who are bereft of allies should back down when confronted by stronger states” (pp. 2–3). The 133 regime changes in Willard-Foster’s study, however, testify that the weak regularly defy the strong—and pay the price for it.

Willard-Foster seeks to explain why weak targets resist strong coercers and, further, why the strong turn specifically to regime change to resolve the dispute. (A third question she addresses is what kind of regime change—full or partial—interveners enact when they undertake FIRC. I leave this question aside for brevity’s sake.) Although the burgeoning literature on FIRC is replete with theories of why states target others for regime change, including economic disputes, ideological differences, shifts in the balance of power, adversary leaders who are deemed incapable of upholding agreements, competition between rivals over buffer states, and establishing and maintaining territorial spheres of influence, almost all of them explain only why two states would enter into a dispute but not why one of them would choose to overthrow the other’s government rather than simply coerce it to change its policy.

Willard-Foster’s answer is that leaders who face powerful domestic oppositions are both hard to coerce and easy to overthrow, which leads coercers to calculate that FIRC may be cheaper than coercion. When the opposition is strong, making concessions to the coercer is likely to endanger the leader’s political survival because it signals weakness at home, which emboldens a leader’s internal foes and may trigger them to launch a bid to overthrow her. Leaders facing this situation are thus likely to resist the adversary’s demands. Even in the unlikely event that such leaders agree to make concessions, however, the coercer will likely need to invest heavily in enforcement mechanisms because these leaders have incentives to renege on the deal to lower their vulnerability to domestic challengers. Because a powerful opposition exists in the target state, however, the coercer is likely to believe that regime change will be cheap and easy, since alternative leaders are available who may be willing to exchange political concessions for the coercer’s support in a bid for power. As Willard-Foster summarizes, “domestically weak leaders should be especially prone to FIRC. Their domestic vulnerability increases the stronger power’s expected costs of obtaining a settlement with them, while simultaneously decreasing its expected costs of overthrowing them” (p. 6).

Willard-Foster’s argument is parsimonious and intellectually appealing because it explains both the target’s refusal to capitulate and the coercer’s belief that regime change will be easy with a single variable: the target’s domestic opposition. She finds support for the argument in a quantitative analysis of attempted and successful FIRCs over the past two centuries as well as a series of paired comparative case studies in which one country experienced regime change while the other did not: Guatemala and Bolivia (1952–1954); Hungary and Poland (1956); and Iraq and Libya (2003). The result is an impressive piece of scholarship that, along with Lindsey O’Rourke’s 2018 book Covert Regime Change, advances our understanding of an important phenomenon.

Willard-Foster, however, could have made her account of regime change more persuasive in three ways. First, because measuring the strength of the domestic opposition in an objective way ex ante is difficult, in the quantitative analysis Willard-Foster opts for two imperfect proxies: the number of times a leader was forcibly removed from office in the prior decade and the magnitude of political change in a country, as measured by the average change in the country’s Polity score over the previous five years. Although Willard-Foster finds significant positive correlations between these variables and the likelihood of regime change, because neither has strong internal validity, her inferences would have been stronger had she demonstrated that targets of regime change with high scores on these variables actually had significant domestic opposition.

Second, Willard-Foster could have considered alternative explanations why weak targets might resist demands from strong states. Willard-Foster argues—plausibly—that leaders fear making concessions because doing so will empower the domestic opposition. Yet it is also plausible that such concessions could weaken leaders with their domestic supporters or simply clash with their own consciences, each of which could cause them to refuse to back down. Both of these possibilities arise in Willard-Foster’s Guatemala case (pp. 128 and 111, respectively). Another reason that weak states refuse demands from stronger adversaries is that they fear that acquiescing will invite further challenges (see Todd Sechser’s article “Goliath’s Curse: Coercive Threats and Asymmetric Power” in the Fall 2010 issue of International Organization). Leaders of weak states thus resist threats from powerful states to build a reputation as a tough type to deter additional demands. Ruling out these alternatives for the target’s resistance would have strengthened Willard-Foster’s proposed causal mechanism.

Finally, Willard-Foster could have addressed a potential endogeneity problem: rather than a leader’s domestic opposition causing regime change, an intervener’s desire for regime change might produce a domestic opposition. States interested in regime change are often able to find somebody to put a domestic face on a foreign coup, whether it is an exiled former leader, political dissident, or ambitious military officer. Indeed, Willard-Foster hints at the possibility that domestic opposition in target states may be the creation of outside powers. She writes, for example, that interveners seek opposition groups that share their policy preferences but notes that this “requirement… is often easily met, as opposition groups may willingly compromise their policy positions to attain foreign assistance in securing power” (pp. 38–39). Because no society is without some political opposition, however, it seems possible that any group, no matter how weak or fragmented, would suffice to facilitate regime change so long as it agreed to accept the foreign power’s help. If true, this would undercut the argument that strong opposition groups are needed to trigger regime change. Decisions for regime change may thus precede—and be independent of—an intervener’s location of a willing domestic partner in the target state.

None of these quibbles should detract from Willard-Foster’s achievement in Toppling Foreign Governments, which provides the most powerful theory yet for understanding why some disputes end in regime change while others do not.