As the new century dawned, a panic engulfed Britain. British companies were being sold off to foreign capitalists, all hailing from the same rising power. These capitalists drew on their emerging nation’s vast wealth to pioneer new systems of mass production, and deploy advanced technology, which left British craftsmen struggling to compete. Hubs of British infrastructure were rapidly bought up. Newspapers and billboards warned in stark terms that Britain risked selling out its sovereignty and security to a foreign power.

This was the situation at the turn of the 20th century when the British press was full of warnings about an ‘American invasion’. The Daily Mail columnist Frederick A. McKenzie painted an ominous picture of the average British citizen rising from his New England bedsheets, pulling on his Boston boots, fastening his Connecticut braces before travelling to work on his New York-designed electric tram and arriving at his office to sit on his Nebraskan swivel chair in front of a Michigan roll-up desk to begin working on a Syracuse typewriter. This was journalistic hyperbole that went well beyond the reality of the time. Yet it encapsulated the fears widespread among British industrialists, politicians and the wider public, as well as across much of the rest of Europe.

The ‘American invasion’ of European markets also aroused fears among strategic thinkers in the United States. The astonishing rise in the nation’s industrial output since the American Civil War had not been accompanied by a comparable increase in the nation’s defence capabilities or its foreign policy objectives. In an age of heightened imperial rivalry between the European great powers, when they were acquiring colonies across Africa and Asia, American politicians and pundits expressed fears that their own country’s wealth and lack of military power might leave it vulnerable. Even as the United States began to strengthen its navy and turned to its own colonial expansion in the Caribbean and Pacific, these concerns remained. Warnings continued to abound that America’s relative lack of naval and military strength when compared to the other great powers, coupled with its domestic protectionism and the increasingly aggressive attempts by its industrialists to expand into overseas markets, would encourage a backlash or tempt the Europeans to encroach on the US’s traditional sphere of influence.

Foremost among those urging Americans that they needed to be militarily and physically prepared to defend their security and interests against all rivals was Theodore Roosevelt. As Colonel Roosevelt of the ‘Rough Riders’, he had helped drive Spain out of Cuba in 1898 and initiated the American surge to great power status. His political fortunes were transformed. The charge that began with Roosevelt’s assault on Kettle Hill would, by the end of the year, take him to the New York governorship, then to the vice-presidency in 1900 and finally, the following year, after William McKinley’s assassination, to the White House as the youngest president in American history.

During Roosevelt’s presidency, the US took significant steps to ensure its military power, particularly at sea, was commensurate with its wealth. It also emerged as a critical arbitrator in great power politics outside the Western Hemisphere for the first time. Yet Roosevelt remained acutely conscious throughout his presidency that the overwhelming majority of Americans, and their representatives in Congress, did not believe that the US had a vital stake in international affairs. Nor did they share his commitment to developing and maintaining the instruments of power that were necessary to safeguard not only America’s immediate prosperity and security, but also to help uphold the broader international order on which both rested. Crucial to Roosevelt’s attempt to bridge the gap between his vision of assertive American global leadership and the reluctance of Congress to assume that role was his command of the ‘bully pulpit’, a term that he originally conceived and which captured his conviction that the presidency provided a national platform from which to exert political and moral leadership. He would deploy his innovative style of presidential rhetoric to explain to the public what he believed its global role should be and to pressure Congress into passing legislation that would develop the material resources that were necessary to carry it out.

In pursuit of this, in his inaugural Address to Congress, Roosevelt invoked the dictum that ‘the surest way to invite national disaster is for a nation to be opulent, aggressive and unarmed’. It was a message that he impressed on his countrymen throughout his two terms in office as he helped transform his nation into a global power. Roosevelt’s warning about the dangers of military unpreparedness in an age of economic protectionism and great power competition remain as pertinent as ever.

Roosevelt came of age politically in an era when the US was rapidly emerging as the world’s most advanced industrial economy. In 1850 both Britain and France produced one and a half times more than the US – within 40 years the US was producing as much as those two combined. Its manufacturing output was the largest in the world. Yet within ten years of the Civil War, the vast Union army had shrunk to fewer than 30,000 men. The US navy was not only inferior to those of pretty much every major European state but also those of some Latin American republics. In 1888 the US navy was so dilapidated that it was forced to back down in a dispute with Chile, with Washington fearing that Santiago possessed the superior fleet.

It was the following year that the US began to redress its naval deficiencies, and Congress was soon authorising the construction of three battleships, which would enable it to dominate its own hemisphere and begin to compete with the capital ships of the major European navies. These developments were given intellectual reinforcement by the naval theorist Alfred Thayer Mahan, who published a series of works over the next decade urging the US to emulate Great Britain as a maritime power. Mahan argued that the new capital ships would need overseas coaling stations, an interoceanic canal and for these acquisitions to be supplemented by a substantial merchant marine that would ensure the overseas trade required for sustained national prosperity.

Despite America’s industrial might and the conspicuous wealth of its robber barons during the Gilded Age, fears were growing about the future of its economy. The most famous jeremiad was sounded by Frederick Jackson Turner. In an address to the American Historical Association in 1893, he argued that the ability to expand and occupy new territories was vital to the health of American democracy. Turner suggested that the final settlement of the West and the disappearance of the frontier would have dire consequences for the American way of life. New frontiers and opportunities would need to be found beyond America’s borders. As Turner declared, with the US ‘fully afloat on the sea of worldwide economic interests we shall soon develop political interests’. The Panic of 1893, devastating for the economy, seemed to confirm the urgent appeals of Mahan and Turner. ‘Expand, or explode, is a fundamental law’, as one historian put it, ‘and America, bursting with power, was prepared to follow its dictates.’

For the influential New Left group of historians that dominated American college campuses in the late 20th century, it was the voracious search for overseas markets to offload its surplus products that motivated the US to become an imperial power. Their argument was that this not only propelled the US into war with Spain in 1898, acquiring overseas colonies in the Pacific and Caribbean in its wake. More importantly, it also led to an ‘informal empire’ with the US assuming economic and political control over nations without the need to impose direct colonial rule. Confident in the strength of the American economy, so the argument went, policymakers were convinced that, backed by an aggressive foreign policy, this would ensure the nation’s pre-eminence in global markets.

The argument that these economic interests drove US global strategy is, however, greatly overstated. It is true that a number of politicians, manufacturers and agrarian businessmen urged the capture of foreign markets and warned of the consequences unless buyers were found for America’s surplus goods and produce. But it is hard to see much impact of this rhetoric on government policy. America’s merchant marine continued to languish. Despite expansion into Asia prompted by visions of a vast China market, by 1900 the whole of that continent only accounted for five per cent of US exports. The vast majority still went to Europe. And calls for lower tariffs to stimulate foreign trade were fiercely resisted by the dominant Republican Party, who feared pressure for reciprocal tariff reduction on America’s own rich, domestic market. Above all, alarm at production outstripping American domestic consumption proved exaggerated. Even as US exports expanded five-fold at the turn of the 20th century, they remained about eight per cent of American GNP, vastly less than the 26 per cent it comprised in Britain.

Given that exports constituted a limited proportion of America’s economy, and considerably less than it had done even earlier in the 19th century, the idea that the search for markets was the fundamental driver of the more ambitious global role that the US began to assume at the beginning of the 20th century is unconvincing. That’s not to say that economic issues did not play a role. Given the vast size of the US economy, even eight per cent of its GNP was still hugely consequential for America’s trading partners. This was why, across Europe, the French intellectual Henri Hauser observed that, at the start of the 20th century, ‘one hears nothing spoken of in the press, at meetings, in parliament, except the American peril’. In 1901 the British journalist W.T. Stead brought out his bestselling The Americanization of the World, which prophesied that the whole world would one day become America’s commercial colony.

That same year, the influential geopolitical thinker Brooks Adams, scion of the family that produced two presidents, warned his countrymen that the ‘present policy of the United States’ risked ‘forc[ing] a struggle for subsistence of singular intensity, upon Europe’. Adams believed that ‘war [was] only an extreme phase of economic competition’ and the current ‘international competition, if carried far enough, must end in war’. That was because the United States had ‘devised a mechanism which holds her rival as in [a] vice’ and that was its prohibitive tariff. By restricting access to its domestic market, while selling ‘their surplus [to] foreigners at prices with which they cannot cope’, it was no wonder, Adams suggested, ‘the European regards America as a dangerous and relentless foe’.

Either there must be compromise – by which Adams meant granting the Europeans reciprocal access to American markets – or war, or ‘else America must be so strong that war is deemed too hazardous to be attempted’. No longer could the US rely on its ‘geographical position’ as security – retreating tortoise-like back into its shell was not an option. Instead, for the European great powers, the US was ‘the fairest prize to plunder since the sack of Rome’. That’s because the United States, with its high external tariff, high moral talk of ‘open doors’ for trade, but low military preparedness was showing itself to be ‘opulent, unarmed and aggressive’. A highly dangerous combination.

These words resonated with Adams’ friend, Theodore Roosevelt, then serving as the nation’s vice-president. Like Adams, Roosevelt feared that excessive materialism inculcated a timidity that weakened civilised nations and left them vulnerable to attack from less advanced, more warlike states. Back in 1891 he had written, in words reminiscent of Adams, of his concern that too many of his countrymen had become ‘traders and merchants who have forgotten how to fight, the rich who are too timid to guard their wealth, the men of property, large or small, who need peace, and yet have not the sense and courage to be always prepared to conquer it’.

Roosevelt was more optimistic than Adams that this could be remedied. He was strengthened by his supreme belief in ‘character’ – both individual and national – to offset any weakness that accompanied material advancement. Domestically, while never a radical, he evinced an increasing commitment to using the power of the state to regulate the market and redress excessive concentrations of wealth. Externally, his principal concern was in making Americans wake up to what he called the ‘utter inconsistency of making this nation [at once] the [world’s] foremost commercial power and of disarmament in the face of an armed world’.

After being elevated to the presidency by an assassin’s bullet, he had the ideal ‘bully pulpit’ to impress his views on Congress and the wider public. As the leader of a Republican Party that was ideologically committed to the tariff, he would go no farther than to treat reciprocity as the ‘handmaiden of protection’ and accept it only ‘so far as it can safely be done without injury to our home industries’. As a result, he placed even greater stress on the corollary that Americans ‘must either build up and maintain an adequate navy or else… accept a secondary position in international affairs, not merely in political, but in commercial matters’.

For a fully-fledged patriot like Roosevelt that was not an option. But his was a broad nationalism. His concept of the national interest was not the limited one employed by international relations scholars – that of purely promoting US interests over and above other nations – but a more traditional and all-encompassing notion of the public interest that embraced both nationalism and idealism.

He told Americans that they could no longer remain ‘opulent, aggressive and unarmed’ because ‘we have reached the stage where we must play a great part in the world’. Roosevelt told Americans that with great power came great responsibilities. These involved not only policing the Western Hemisphere to ensure that European powers had no excuse to use the collection of debts to intervene themselves – the notorious Corollary to the Monroe Doctrine – it also involved diplomatic interventions against the state sanctioned persecution of Jews in Tsarist Russia and Armenians in the Ottoman Empire. It was no coincidence that, in this first era of globalised trade and relatively unencumbered movements across national boundaries, these were the only two major powers that required passports.

Roosevelt was also the first American president to declare (and act) on the belief that his country’s duties extended not only ‘across the Occident, [but] in the Orient as well’. He welcomed Japan’s rise to great power status as a constitutional, free-trading state, contrasting it with the autocratic Russia that threatened the Open Door in China. He helped ensure that Tokyo, unlike after the 1895 Sino-Japanese War, secured the fruits of its victory during his Nobel Peace Prize-winning mediation at the Portsmouth Peace Conference. He again employed his favourite watchwords when, after Japan’s victory over Russia, he chastised Californian politicians for insulting Japan, by seeking to restrict Japanese immigration and discriminating against its citizens, while refusing to build up the US Navy to protect its relatively defenceless coastline.

For a figure who had been so pugnacious in the 1890s that he had dreamed of leading a cavalry charge to capture Canada, the responsibility of the presidency reined in his most aggressive instincts. But he also knew his countrymen, and knew their commercial ambitions, and that in pursuit of them they could, in his words, be ‘so high-spirited as to be careless of giving offence’. As a result, the nation must be prepared for any danger that came its way. And Roosevelt was alarmed that, despite his own attempts to get the US to acquire the instruments of power, by the end of his presidency, it still remained ‘of all the nations of the world, the one that combines the greatest amount of wealth with the smallest ability to defend it’.

By that time, he had come to recognise that the US needed to be armed, not just to protect its own security, but also to help uphold a wider global order, on which both its political and economic interests depended. At the outset of his presidency, Roosevelt was uncompromising in his diplomatic disputes with Britain. He was determined to establish US hegemony in the Western Hemisphere, assume sole proprietary over the construction of an interoceanic canal across the Central American isthmus, and to redraw territorial boundaries that prioritised American claims over those of British colonies.

Having successfully forced British policymakers to comply with his demands, Roosevelt increasingly came to recognise that America’s own security and prosperity was safeguarded by the Royal Navy and its protection of sea lanes within a wider Free Trade system. That had largely ensured the US could have the best of both worlds, able to export its products to the world’s largest markets while maintaining its home tariff. But the ‘equilibrium’ that Britain had maintained in the world’s financial system, and the ‘balance’ it had helped ensure between the great powers in Europe, was increasingly at risk with new great powers emerging, particularly Germany. This meant the US might be called on to step in because, in Roosevelt’s words, it was increasingly becoming ‘the balance of power of the whole world’.

During his own presidency, Roosevelt was unable to convince Americans that they must be prepared to assume that role. It would take two world wars to bring Roosevelt’s central lesson home to Americans – that safeguarding their wealth and security went hand in hand with a duty to conserve a wider global order on which the peace and prosperity of other like-minded nations rested.

Roosevelt’s warning continues to resonate. The US is, of course, far from unarmed, but in an era of growing economic competition – marked by trade wars, tariffs and aggressive rhetoric – it is unclear that the US and its allies have sufficient capabilities to deter a multitude of authoritarian challengers across several theatres. Roosevelt’s warning is even more of a clarion call for Europe, and particularly for the European Union. The continent remains relatively wealthy, increasingly (and rightly) assertive in its posture towards Russia, but still, particularly without American support, insufficiently armed.

At the beginning of the 20th century, Roosevelt’s warning helped inspire his country to both rearm and avoid gratuitously offending rivals in a dangerous world. Today, at another critical juncture, his words remain just as relevant.