Why did the United States foreswear territorial annexations in the late nineteenth century, even as its economic and military power grew? This is the central question of Richard Maass’s theoretically innovative and deeply researched new book. His answer is that US policy makers gave more weight to the domestic and normative consequences of potential annexations more than their relative profitability when making the choices that they did. In particular, they “feared the domestic impact of absorbing large alien populations into their democratic institutions,” and thus US expansion was “consistently targeted [toward] land rather than people” (p. 9). Once tracts of sparsely populated territories were no longer available, the United States became “disinterested in annexing its neighbors,” an outcome Maass characterizes as “truly exceptional in world history” (p. 11) and one with long-lasting consequences for US foreign policy and for broader norms of territorial conquest.

Maass develops this narrative through the lens of what he calls “domestic impact theory” (p. 23). This theory argues that leaders have two concerns about the domestic impact of territorial annexations. The first is that annexations might “weaken their domestic political position” by rendering their government a “less cohesive corporate actor” (p. 28). The second is that annexations can “worsen their state’s social and political institutions” by “distorting the state’s domestic political institutions” (p. 29). Maass contends that these anxieties will be particularly salient both for democratic countries, where annexation threatens to change “the makeup of society and hence of the electorate” (p. 31), and for xenophobic leaders, who “see alien peoples as fundamentally inferior…[and thus] unfit to join their state” (p. 36). Maass examines the impact of democracy and xenophobia across 23 cases of US territorial expansion from the American Revolution through the Spanish-American War. When domestic constraints were minimal, as was the case with the Louisiana Purchase and Oregon and California cessions, he finds that annexation was undertaken with enthusiasm. When there were concerns that annexations would add large alien populations to the United States, as was the case with eastern Canada, southern Mexico, Cuba, Puerto Rico, and the Philippines, policy makers avoided annexation, despite its potential economic benefits.

Maass has written a book that is theoretically ambitious and empirically expansive, and the historical and archival evidence he marshals is rich, impressive, and ultimately convincing. I particularly appreciated the section in which Maass explained where his interpretation of events differs from the existing historiography (pp. 18–22) and where he judiciously compares the predictions of his “domestic impact theory” to the alternative “profitability theory” across all of his cases (pp. 199–203). It is impossible to read the myriad quotes from US policy makers denigrating the character of Mexicans, Cubans, Puerto Ricans, and Filipinos and not conclude that race has played a fundamental role in shaping how the United States engaged in territorial conquest. It is a dark irony, as Maass observes (p. 207), that US policy makers’ acceptance of their neighbors’ political independence stemmed from such debased motives, that it was the country’s intolerance and illiberalism that acted as a brake on potential expansion and exploitation.

Of course, as with any ambitious book, there are places where the theory could be sharpened. Maass acknowledges, for example, that domestic costs must be weighed alongside the military costs and material benefits of any potential annexation (p. 39), but he does not provide a clear accounting of how policy makers should balance these three considerations. Presumably there are cases where leaders accept the domestic political costs of annexation because they believe they are outweighed by potential security or economic benefits. Tsarist Russia’s annexations in the Caucasus and Central Asia, Austro-Hungarian expansion in the Balkans, and France’s conquest of Algeria could all be read in these terms. Perhaps nineteenth-century American policy makers were unique in how they stressed the domestic costs of annexation, because they already possessed abundant territory and resided in a relatively secure neighborhood and thus did not need to gamble to acquire more territory. President Polk was unwilling to run any “military risks” (p. 107) to secure a large Oregon cession, and President Grant was hesitant to make any demands on western Canada that might “undermine U.S.-British relations” (p. 116). The United States may have been a picky eater simply because it lacked the appetite.

It is also unclear why the domestic costs of annexation might appear greater in some cases compared to others. When do leaders see democratic institutions as particularly fragile? When are xenophobic attitudes particularly powerful? Do policy makers tend to place greater emphasis on the practical institutional challenges posed by annexations or their normative implications? Maass suggests that xenophobia was an “especially powerful” (p. 46) component of annexation debates in the late nineteenth century, but it is unclear when or why Americans’ racial attitudes hardened. There are also places in the case narratives where policy makers seem to be driven less by a concern about the viability of America’s democratic institutions than by a consideration of their own party’s political interests. The story of debates surrounding the Louisiana Purchase, the Florida and Texas cessions, and the potential annexation of Cuba is essentially one of southern expansionism, northern opposition, and regional rivalries over the future of slavery. Southern success in some of these cases seemed to have less to do with the absence of domestic costs than Virginia politicians’ “institutional dominance” (p. 56) and “firm grip on the federal government” (p. 60). Especially in the antebellum period, US politicians appeared less like democracy’s sentinels and more like sectional warriors, willing to sacrifice national cohesion if the spoils of annexation flowed disproportionately to their constituents.

One final question concerns the alternatives to annexation. Maass notes that one of the obvious alternatives is formal imperialism, where a territory is under foreign control but is not integrated into the domestic political institutions of the metropole (p. 3). For a number of democratic countries, whether Britain, France, the Netherlands, or Belgium, imperialism and domination abroad proved perfectly consistent with liberalism and democracy at home. It is unclear from Maass’s narrative, however, why the United States was unwilling to entertain formal imperialism for most of the nineteenth century and then did so somewhat reluctantly after the Spanish-American War. Some of the quotations Maass includes imply that US policy makers may simply have rejected formal imperialism as incompatible with American values. During debates about the Dominican Republic, one Missouri senator warned that imperialism would produce “nurseries of rapacity, extortion, plunder, oppression, and tyranny…and impart to our government a military character most destructive of its republican attributes” (p. 171). In discussions regarding Hawaii, an Indiana senator warned that imperialism “would establish in this great republic by legal enactment the hateful rule of caste, and create an oligarchy under the American flag as tyrannical and brutal as any that ever flourished in the despotisms of the Old World” (p. 184). Maass claims that “the logic of domestic impact theory is not uniquely American” (p. 299), but these quotations suggest that the United States was unusual in the “annexation or nothing” approach it embraced for much of the nineteenth century. Yet the fact that the United States eventually expanded to include Puerto Rico, Guam, Samoa, and 10 other “unincorporated territories” suggests that democratic and republican values were not insurmountable barriers to territorial conquest and formal imperialism in the end.

None of these questions should detract from the overwhelming strengths of this book. Maass has persuasively shown how American annexationist impulses were tempered by considerations of democratic vitality and racial purity. He has shown that the United States’ aversion to territorial conquest is rooted less in its respect for other peoples’ sovereignty than out of concern for its own.