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Waves of Expansion, 1857–Present

The United States today is a “beached superpower.”1 At least in Eurasia, its immense forward presence is a holdover from the World War II and Cold War eras, when US military personnel were sent in their millions to Europe and the Asia-Pacific to defeat fascism and then deter communist expansion. When World War II ended in 1945, the Army alone had around 2,327,000 troops in Europe and the Mediterranean, with an additional 1,791,000 in the Asia-Pacific. Over 450,000 soldiers were deployed overseas in other locations – i.e., the Americas, and Africa, or else were “in transit.”2 Millions more served in the Navy. Few in the US government expected that these would be permanent garrisons. On the contrary, having vanquished the Axis Powers, President Truman moved quickly to bring home as many US troops as possible. Toward the end of 1945, his administration was discharging up to 1.2 million personnel per month from all branches of the military – the quickest demobilization in history.3 Even during the early Cold War, as US leaders accepted the need to retain a significant military presence in Europe and East Asia, officials in the executive branch assured Congress that stationing troops in allied nations was a temporary measure that could and would be reversed once those living in the shadow of the Soviet Union were able to provide for their own defense.4

Yet more than three decades after the Soviet collapse, the United States remains in occupation of around eighty foreign countries and territories. To be sure, the total number of US military personnel based overseas is much smaller today than during the second half of the twentieth century (in the region of 170,000 compared to an average of around 535,000 during the period 1950–2000).5 But at the same time, the geographic expanse of America’s security obligations has increased dramatically in the post-1991 period, with the United States adding bases large and small to its already gigantic military footprint in Europe, East Asia, the Persian Gulf, Africa, and elsewhere. On its face, it is something of a puzzle why the United States chose to remain vastly forward deployed after the Cold War. Why did US officials never make good on their promises to retrench once conditions in Eurasia became more favorable? Why, instead, has the US military footprint expanded? What has been the justification for America’s overseas presence in the absence of a hegemonic competitor?

To answer these questions, it is helpful to view America’s contemporary forward deployments in historical context. For today’s permanent overseas garrisons are only the latest manifestations of US interventionism. Since the mid-nineteenth century, the United States has undertaken at least six waves of overseas expansion, which I define here as programmatic attempts to project power and influence over foreign lands in furtherance of perceived national interests. These waves occurred for a variety of reasons: commercial, strategic, ideological, imperialistic, domestic-political, and defensive. Some resulted in the annexation of new territories, leading to the permanent stationing of forces abroad. Other waves were characterized by interventions of a temporary nature; politicomilitary actions that, once completed, were followed by the total withdrawal of US military personnel. Still other waves of expansion looked likely to be temporary at the outset but morphed into a constellation of indefinite occupations with the passage of time – the World War II and Cold War–era deployments to Europe and East Asia being the most obvious cases in point.

In this chapter, I categorize the six waves of US expansionism as follows. The first wave occurred between 1857 and 1897 and was defined by the seizure of relatively small and predominantly unpopulated island territories in the Caribbean and Pacific. These acquisitions were undertaken for instrumental purposes, such as narrow commercial gain or to meet an obvious logistical need, and were performed by private citizens as well as the US military. A second wave took place between 1898 and 1917, during which era the United States annexed its first populated overseas territories – the Philippines, Guam, Puerto Rico, Panama Canal Zone, and US Virgin Islands – and thereby came to resemble a colonial empire. Of these, only the Philippines and Panama Canal Zone have since been decolonized. This era also saw the United States launch a number of military interventions-cum-occupations in Latin America, the Caribbean, and China. The third wave of overseas expansion happened during World War I and the interwar period (1918–1940), when the US military intervened decisively in European affairs to defeat Imperial Germany and assist in the imposition of a postwar settlement at Versailles, only to withdraw its military forces from the troubled continent. The fourth wave occurred during World War II and its immediate aftermath (1941–1949) and saw the United States undertake a globe-spanning effort to defeat the Axis Powers, then wrestle with the questions of whether, how, and how quickly to retrench from Europe and East Asia amid uncertainty about the threat posed by the Soviet Union. The fifth wave happened during the Cold War (1950–1989), when US leaders accepted the need to occupy parts of Western Europe and the Asia-Pacific (and later the Persian Gulf) on a permanent basis. The Cold War was defined by massive US military interventions abroad, with the United States fighting two devastating hot wars against communist rivals – in Korea and Vietnam – and electing to wage proxy wars in places such as Angola, Mozambique, and Afghanistan. The sixth and final wave of overseas expansion has lasted from 1990 to the present day, as the United States has chosen time and again to wield the mammoth forward deployments inherited at the end of the Cold War in service of expansive aims: an enlarged NATO alliance in Europe; nearpermanent warfighting in the Middle East, North Africa, and Central Asia; and an ambitious military-strategic “pivot” to the Indo-Pacific, all justified as necessary to uphold US national interests and the associated rules-based (“liberal”) world order.

The chapter concludes by making two descriptive points: (1) that the United States does have some experience of retrenchment following waves of expansion, and has exercised meaningful restraint at various points in its history as a great power; but (2) the tendency for Washington to resist retrenchment and instead preserve (repurpose) its overseas military deployments has become more pronounced with the passage of time. To be sure, the exceptions to this general trend toward permanent military deployments should not be minimized – the withdrawal of forces from Taiwan in the 1970s, the handover of the Panama Canal Zone, the downsizing of US forces in Europe during the 1990s, and the exit from Afghanistan in 2021, for example, were all appreciable instances of retrenchment. Each offers clues regarding the conditions under which the US political system is capable of supporting drawdowns in overseas forces. But the broad pattern described in this chapter is striking, and important: viewed in the longue durée, the United States has been gathering overseas security commitments since the 1850s – and it has become much less adept at shedding these obligations as time has worn on.

Commerce, Coal, and Colonization: 1857–1897

The United States has always been an expansionist power.6 When the Thirteen Colonies declared independence from Britain in 1776, they did so claiming jurisdiction over the Northwest Territory, an enormous expanse of land that was subsequently settled by US citizens and became incorporated into the United States proper as the present-day states of Ohio, Indiana, Illinois, Michigan, and Wisconsin, as well as parts of Minnesota. In 1805, the United States almost doubled its land area when President Jefferson agreed to purchase the Louisiana Territory from France. This was followed by the acquisition of the Floridas (1819), Texas (1845), and the Oregon Territory (1846). In 1848, the United States defeated Mexico in the Mexican–American War and annexed around 55 percent of Mexico’s prewar territory as part of the treaty of peace. With this gargantuan act of conquest, the United States completed a westward continental push that few could have anticipated at the time of its founding. In just over half a century, the United States had grown to encompass the entire middle portion of the North America – from “sea to shining sea.”

America’s overseas conquests unfolded on a different timeline, however. The origins of this story can be traced to the Guano Islands Act of 1856, which authorized private citizens to seize islands on behalf of the US government, so long as the islands in question were unclaimed, unpopulated, and contained deposits of guano (bird excrement).7 With the passage of the Act, enterprising US citizens moved to claim several small island territories in the Pacific Ocean, including Baker Island, Howland Island, Jarvis Island, Kingman Reef, Swains Island, and the Johnston Atoll. All these islands were later made into unorganized, unincorporated US territories and remain so today. In the Caribbean, the United States claimed sovereignty over the Swan Islands, Roncador Bank, Navassa Island, Bajo Nuevo Bank (Petrel Island), Quita Sueño Bank, and Seranilla Bank – all tiny island outcrops of little...