In his revised PhD dissertation, Matthew Karp, Assistant Professor of History at Princeton University, puts the history of American slavery in the antebellum period in an international rather than domestic context. Political and intellectual leaders in the South believed that to protect the “peculiar institution” they did not only have to fight off domestic opposition to slavery, but also ensure that an international environment conducive to the maintenance of forced labor was maintained. Their insistence on states’ rights within the union, commonly emphasized by scholars of the era, should therefore not be misinterpreted as an end in itself, as Karp points out, because in terms of foreign policy they were actually proponents of an increase of the federal government’s power, believing that only a strong executive could defend Southerners’ slaving interests around the globe with maximum effect. “In domestic politics, the ideological commitment to slavery often drove southerners toward a defensive emphasis on states’ rights. In foreign and military policy, the same commitment led to […] unapologetic centralism” (p. 49). Consequently, they sought positions as foreign-policy makers (such as those of the President and the Secretaries of State, Navy, and War) and as diplomats as well as within pertinent congressional committees rather than offices concerned with domestic issues in order to be able to pursue what Karp, using a phrase of Robert Kagan, calls “a foreign policy of slavery” (p. 7). As a result, they exerted a preponderant influence on U.S. foreign policy, as Karp claims. “Nowhere did slaveholders wield their power with more energy or commitment than in the realm of foreign and military policy” (p. 5). This Vast Southern Empire – based on diplomatic correspondence, newspapers, congressional debates, and other documents by leaders of the South – therefore sets out to trace how slave-owners shaped U.S. foreign policy in the three decades before the Civil War to safeguard their slaving interests.
Karp rightly considers the abolition of slavery in the British Empire in 1833 as a decisive turning point, as it marked an international threat to the institution. Before Great Britain emerged as the “great Apostle of emancipation,” as the Southern Patriot in Charleston called her in 1840 (p. 28), slavery had not played a prominent part in U.S. foreign policy. However, once Great Britain lent her prestige and power not only to the suppression of the international trade in human cargo, but also to the abolition of slavery itself, Southern slave-owners felt the need to bolster other slave regimes such as those in Cuba and Brazil, the two largest slave societies in the New World in the mid-19th century, in order to protect the institution at home. Fearing a domino effect if slaves were emancipated in these countries, they wished the U.S. to become an international protector of slavery. As a result, slave-owners such as Lieutenant Matthew Fontaine Maury and Secretary of the Navy Abel Parker Upshur worked hard to build up and modernize the navy such that the U.S. could defend slavery against Great Britain throughout the Western Hemisphere and keep the Royal Navy away from America’s southern coast where the British might incite slave rebellions. “At sea, at least, federal power was not a danger to be feared but a force to be utilized,” as Karp explains (p. 35). Southern leaders also pushed for the annexation of Texas and embarked on a war against Mexico in order to protect slavery in the Southwest rather than because of expansionist desires. In turn, they chose not to support filibustering missions to Cuba, fearing that an American invasion of the Caribbean island with the aim of annexing it to the U.S. could trigger the emancipation of the slave population by the Spanish governor, “spoiling the fruit” of the expansionist war “for good” (p. 187).
While the South was increasingly driven into the defensive in domestic politics in the 1850s, it became more confident about its place in the global economy, believing that the products of slave labor such as cotton, sugar, coffee, and tobacco were essential for the industries of Europe and interpreting the rampant European imperialism in Africa and Asia, the introduction of “coolie” work regimes in the West Indies, and the flowering of scientific racism as an acknowledgment that abolitionism had been a mistake and that the future belonged to bound labor, as Karp argues in the second part of his book. “In the decades before the Civil War, slaveholders organized U.S. foreign policy around the effort to defend slavery as a vital element of global progress” (p. 256). However, when Abraham Lincoln won the 1860 presidential elections, Southerners lost access to the foreign-policy making power of the federal government and therefore decided to found their own confederacy whose constitution would give the Southern government sweeping powers to defend slavery at home and abroad. “Secession did not produce a flight away from central authority but the eager embrace of a new and explicitly proslavery central authority.” (p. 244)
Karp’s lucidly-written and well-researched book forms part of a contemporary trend in the historiography of the antebellum South, which does not regard slaveholders as anachronistic romantics who fought a rearguard battle against economic modernization processes, but as self-confident capitalists who sought to build a slaveholding empire using the power of the federal government to advance their international agenda. By examining episodes such as the seizure of Monterey by the U.S. Pacific Squadron in 1842 or the informal military alliance between the U.S. and Spain in defense of slavery in Cuba in 1843, which have previously received scant attention, This Vast Southern Empire also adds original insights to recent works in U.S. diplomatic history that have investigated how the federal government continuously acted as an agent for the slaveholding interests of the South in its handling of foreign policy.
Karp’s thesis that Southern slave-owners did not pursue territorial expansion and insist on states’ rights on principal grounds, but opted for whatever course was most suitable in a particular context to protect the institution of slavery is convincing and satisfactorily proven, as is his claim that they identified foreign policy as a powerful tool to advance their slaving interests. While Karp’s emphasis on Southerners’ international outlook is fascinating, one is still left wondering about the domestic effects of their foreign policy. How did Northerners react to Southerners’ disproportionate influence on American foreign policy? Were Southerners able to rally the nation behind their diplomatic agenda by exaggerating the British threat? Did Northerners accept Southerners at the helm of U.S. foreign policy in turn putting a larger emphasis on determining domestic policies? Was the focus that Southerners placed on foreign policy in the end misguided, since they failed to maintain their power base at home, a Northern-based anti-slavery Republican Party winning the elections of 1860 and consequently assuming command over America’s military that Southerners had previously helped modernize and enlarge? Drawing attention to these open questions is not a criticism but, to the contrary, a call for scholars to engage with Karp’s thought-provoking and thesis-driven book, which deserves a wide readership, as it complicates our understanding of how Southern slaveholders perceived the world and shrewdly demonstrates that debates over slavery were never merely about the domestic, but also about the global balance of power.
 Robert Kagan, Dangerous Nation. America’s Foreign Policy from Its Earliest Days to the Dawn of the Twentieth Century, New York 2006, chapter 7.
 Walter Johnson, River of Dark Dreams. Slavery and Empire in the Cotton Kingdom, Cambridge 2013; Edward Baptist, The Half Has Never Been Told. Slavery and the Making of American Capitalism, New York 2014; Sven Beckert, Empire of Cotton. A Global History, New York 2014.
 See, above all, Don E. Fehrenbacher, The Slaveholding Republic. An Account of the United States Government’s Relations to Slavery, Oxford 2001.