The first wave of imperial conquest was on the mainland of what is now the United States, achieved primarily through purchase from other imperial powers, and the conquest of the indigenous inhabitants. Those indigenous inhabitants who had not perished through military conflict or disease were wrenched from place to place, their lives and livelihoods dictated by the federal government. It was a pattern that would be repeated as the United States expanded its territories off the mainland.

The Spanish–American War of 1898 was the turning point for US imperialism. Internal expansion gave way to external, with the destiny of the post-Civil War nation now seen to be in the Caribbean and in the Pacific. Leading the charge, sometimes literally, was Theodore Roosevelt. Empire, in his eyes, was America’s destiny. These years saw the United States take over the remnants of the once powerful Spanish empire, expanding into Cuba, Puerto Rico, Guam, and the Philippines. Accompanying these occupations was a powerful sense of racial superiority, and a ‘civilising mission’ similar to the British Empire’s global engagements. At the same time, debates raged from Congress through to the popular press about whether these subject peoples could be incorporated into the United States:

This was, in other words, a different kind of expansion … not taking land and flooding it with settlers, but conquering subject populations and ruling them. ‘It is one thing to admit scattered communities of white, or nearly white, men into the rights of citizenship,’ one writer put it, ‘but quite a different matter to act in the same way with a closely packed and numerous brown people.’ Or as the sceptical Speaker of the House put it, less politely, ‘I s’posed we had niggers enough in the country without buyin’ any more of ’em.’

The subject populations that fell under the dominion of the United States would endure much under its rule. In a particularly harrowing section, Immerwahr details the activities of Cornelius Rhoads in the 1930s, who viewed Puerto Rico ‘as an island-size laboratory’ for his medical theories: ‘a place to try out ideas while facing few consequences’. In a precursor to the infamous Tuskagee experiment, Rhoads would refuse to alleviate the conditions of hookworm-infected patients suffering from anaemia, preferring to track the progress of the disease. Writing to a colleague in Boston, Rhoads stated that the Puerto Ricans were:

beyond doubt the dirtiest, laziest, most degenerate and thievish race of men ever inhabiting this sphere … what the island needs is not public health work, but a tidal wave or something to totally exterminate the population. It might then be liveable. I have done my best to further the process of extermination by killing off 8 and transplanting cancer into several more. The latter has not resulted in any fatalities so far.

Rhoads would go on to engage in chemical-weapons testing during World War II, sometimes on willing volunteers, sometimes on prisoners. Out of this research came the beginning of chemotherapy, and consequent accolades for Rhoads. A major medical prize was named after him by the American Association for Cancer Research, until protests by Puerto Ricans in 2003 saw the name changed.

The United States was the only nation that emerged from World War II stronger than when the war began. A new international order had been formed, as former European colonial empires collapsed and transformed into the proxy battlefields of the Cold War. America’s imperialism would be as much cultural and economic as martial during what was dubbed ‘the short American century’. Terms like ‘coca-colonisation’ were coined to describe the spread of American culture and ideals around the globe. Nowhere is this better covered than in the chapter ‘Language is a Virus’, which explores the intertwining of American imperialism and the growth of English as the global lingua franca. The US global influence includes roughly eight hundred military bases, many located in nations with which they have previously been at war with: Germany, Japan, the Philippines, as well as ostensible allies like Saudi Arabia. The consequences of these extended military presences have led to what Chalmers Johnson referred to as ‘blowback’ in his book of the same name. The most apocalyptic form of this blowback against American imperialism came on 11 September 2001. The response, quickly called ‘the war on terror’, shared some similarities with the imperialism of old, with ‘American values’ standing in for ‘civilising missions’. But George W. Bush and his cabinet were keen to emphasise that they were a ‘liberating power’, not an imperial one. Few were convinced.

In 1816, Thomas Jefferson wrote to John Adams that: ‘We are destined to be a barrier against the returns of ignorance and barbarism. Old Europe will have to lean on our shoulders, and to hobble along by our side, under the monkish trammels of priests and kings, as she can. What a Colossus shall we be when the Southern continent comes up to our mark!’

Daniel Immerwahr has provided a timely, succinct account of exactly what this ‘Colossus’ has done. While the occasional bouts of humour seem a little forced (interesting though the subject may be, no chapter should ever be called ‘Everything You Always Wanted to Know About Guano but Were Afraid to Ask’), the writing is crisp and focused, providing an ideal entry to a complex topic for the layperson. The work on US imperialism is showing no signs of diminishing in the post-9/11 world. How to Hide an Empire: A short history of the greater United States is a fresh and original contribution to the literature.