‘The prime obligation of the defence of Western Continental Europe rests upon the nations of Europe,’ thundered the former President of the United States. Until those nations paid up and started spending more on their own defence, the US should not ‘land another man or another dollar on their shores’. And if they refused to do so, he suggested the US could pull back from continental Europe and rely on its air and naval forces to defend its homeland and surrounding oceans. Across the Atlantic, there was uproar and anxiety. ‘Where does this leave us poor Europeans?’ lamented an editorial in the Guardian. From the White House, the Democratic President charged his Republican rival with isolationism and lambasted his speech as a gift to Moscow.

This was the situation in December 1950, when former President Herbert Hoover’s speech kicked off what became known as the ‘Great Debate’ over US foreign and defence policy. For almost a decade, indeed practically ever since Donald Trump descended the golden staircase at Trump Tower, we have been in the midst of a new ‘Great Debate’. Just as in 1950, it has centred to a large extent on questions of burden sharing among allies, and whether the US would be better served focusing its attention on Asia and leaving the defence of Europe to the Europeans. It is a debate that would have continued regardless of who won the election.

The original ‘Great Debate’, coming shortly after the passage of the North Atlantic Treaty, was sparked by the decision of Harry Truman’s administration to dispatch a large contingent of US troops to Europe under the command of the D-Day hero and new Supreme Commander of an integrated NATO force, Dwight D. Eisenhower. Alongside Hoover, the principal opponent of the administration’s commitment of ground forces was Robert Taft, the senator from Ohio, whose high standing with his colleagues had earned him the nickname ‘Mr Republican’. Both Taft and Hoover were staunch opponents of the Soviet Union, but they were also concerned about expensive overseas commitments and distrustful of whether Europeans were willing to do enough to help themselves.

With American forces on the backfoot in the Korean War, and the Truman administration already under fire for having ‘lost’ China, their views struck a chord with considerable sections of a war-weary public. A sizeable number of senators from both sides of the aisle shared their concerns about Congress conceding too much power to an over-mighty executive. Underlying all of this was a suspicion that Europeans were taking advantage of the American security guarantee, leaving a sense that the US would be left carrying the bag for the continent’s defence.

The ‘Great Debate’ ended in a clear victory for the Truman administration. Congressional approval was secured for sending US troops to Europe. And Eisenhower returned from Europe to first beat Taft to the Republican nomination and then capture the presidency. As president, Eisenhower helped to entrench Truman’s national security doctrine of a forwardly deployed presence of US troops overseas, the establishment of a system of international alliances and the concentration of unprecedented power in the executive, including control over the decision to deploy nuclear weapons.

This should not disguise the level of ambivalence that remained among many senior American policymakers about the sustained presence of US troops in Europe. The Senate’s lack of resolve was reflected in Resolution 99, which approved sending troops, but also stressed that Europeans should be responsible for the bulk of NATO’s ground forces. It was envisaged that, in time, the US could draw down its land forces, and that any additional troops would require Senate approval.

This was not simply a concern of sceptics such as Hoover and Taft. It was also one felt by leading officials in successive administrations, as the esteemed Cold War historian Marc Trachtenberg reminded us in a recent policy paper for the Cato Institute. While highly critical of Taft and Hoover in public, Truman’s Secretary of State Dean Acheson privately took the view that long-term it was ‘probably neither practical nor in [the] best interests of Europe or [the] US that there should be a US Commander in Europe or substantial number of US forces on the continent’.

Eisenhower was even more unwavering on this point. While a far more committed advocate of American alliances than Taft or Hoover, he shared their concern that open-ended overseas commitments could financially exhaust the United States. He differed with them over the timing and tactics for drawing down US troops in Europe, but agreed ultimately that a large American contingent could not remain on the continent indefinitely. While commander of NATO forces in 1951, he maintained that ‘there is no defence for Western Europe that depends exclusively or even materially upon the existence, in Europe, of strong American units’. The US could not be ‘a modern Rome guarding the far frontiers with our legions’, and it was imperative that Europeans ‘regain their confidence and get on their own military feet’. This continued to inform his outlook as president. Indeed, he told the NATO secretary general in 1959 that Europeans should be ‘ashamed’ that they were so reliant on the US for their security and expressed fear that they were on the verge of ‘making a sucker out of Uncle Sam.’

Yet, despite his frustrations, Eisenhower did not make any significant drawdown of the US contingent in Europe. Attempts to establish a European Defence Community, which would enable the withdrawal of US troops, were thwarted when the French government, the initial instigators of the idea, changed tack in the face of parliamentary opposition. In particular, the French, less than a decade since the end of the Second World War, resisted German rearmament. Conversely, US strategists came to recognise that only a powerful Germany, complete with nuclear weapons, would be sufficient to allow the US to withdraw its forces while still providing sufficient deterrence to keep the Soviets out. Eisenhower showed an openness to this idea, but his successors, beginning with John F. Kennedy, recognised that neither America’s allies in Western Europe nor the Soviet Union were prepared to accept a Germany with nuclear weapons. The only feasible counterbalance to Soviet power in Europe, for friend and foe alike, was therefore the enduring presence of a forwardly deployed United States, bringing Europe decisively under its nuclear umbrella.

Nevertheless, pressure for the Europeans to step up their spending, and enable at least a reduction in US ground troops, continued to bubble up intermittently, particularly in the Senate. Most notable was the campaign led by Senate Majority Leader Mike Mansfield, a Democrat from Montana, in the late 1960s and early 1970s. Mansfield proposed cutting around half of US troops in Europe. As Mansfield put it in 1970, he saw no reason why 250 million Europeans could not muster the forces to ‘defend themselves against 200 million Russians who are contending at the same time with 800 million Chinese, but [instead] must continue after 20 years to depend upon 200 million Americans for their defence’.

This argument appealed to a considerable number of senators, weary with the ongoing war in Vietnam and concerned about the balance of payments deficit arising from stationing US forces in Europe. But President Nixon’s argument that, ‘as the most powerful member of the Alliance, the United States bears a responsibility for leadership’, helped defeat Mansfield’s proposals. A majority in the Senate shared the fear, privately expressed by Nixon’s National Security Advisor Henry Kissinger, that the Europeans would not step up if the Americans pulled back. It was more likely, Kissinger suggested, that ‘when big brother even appears to falter, the little brethren will not move forward courageously – as we seem to think – but, on the contrary, they will anxiously take several steps backward.’

This argument held sway for the rest of the Cold War. Indeed, it continues to resonate to this day. After the collapse of the Soviet Union, US forces were indeed drawn down in the 1990s, but European governments took advantage of the ‘peace dividend’ to cut their defence spending even more sharply, leaving the continent’s defence weighted yet more heavily on US military power.

By 2011, with the US shouldering roughly 75 per cent of NATO’s defence spending, Secretary of Defense Robert Gates was warning Europeans that their unwillingness to invest sufficiently in their own defence risked dooming the alliance to a ‘dim and dismal future’. Gates was speaking as someone for whom European stability, ‘with NATO as the main instrument for protecting that security – [had] been the consuming interest of his professional life’. For him, ‘the benefits of a Europe whole, prosperous and free after twice being devastated by wars requiring American intervention was self-evident’. His concern, however, was that ‘future US political leaders – those for whom the Cold War was not the formative experience that it was for me – may not consider the return of America’s investment in NATO worth the cost’.

Gates’ fear proved prescient. Since his ascent to become the Republican nominee and then president in 2016, Trump has regularly suggested that he believes the cost of NATO outweighs the benefits. Indeed, these views were evident long beforehand. As early as 1987, during a TV interview with Larry King, Trump declared that ‘if you look at the payments we’re making to NATO, they’re totally disproportionate with everybody else’s’. NATO was taking ‘tremendous advantage’ of the US, according to Trump. Washington’s focus should be on ‘making lots of profit – so-called surplus’ to ‘defend our homeless, and our poor, and our sick, and our farmers’ rather than ‘giving it to countries that don’t give a damn for us to start off with’. More than any other major American political figure since the original Great Debate, Trump has consistently, vehemently and publicly questioned the relevance of NATO and America’s continued commitment to it.

There is no direct analogy between Trump and Truman’s opponents in that earlier clash. While Hoover and Taft were fiscal conservatives, seeking to rein in expensive overseas commitments in pursuit of a more balanced budget, Trump’s scepticism of NATO sits alongside spending plans and tax cuts that are poised to add trillions to America’s already record federal debt, according to the nonpartisan Committee for a Responsible Federal Budget. Neither Hoover nor Taft shared Trump’s mercantilistic approach to trade, nor did they praise any Soviet leader in the way that Trump has Vladimir Putin. But the strategy that Trump’s national security team is supposedly developing for NATO bears a close resemblance to the emphasis on air and naval power, and the same hostility to substantial ground troops, advocated by Hoover and Taft.

Despite fears that a second Trump presidency would lead to the US quitting NATO, a report in Politico, based on interviews with those linked to Trump’s national security team, suggest that what is more likely is a ‘radical reorientation’ of the alliance. Under these proposals the US would maintain its nuclear umbrella over Europe, but, at the same time, drastically reduce its ground forces, ‘significantly and substantially downsizing America’s security role’. This would leave the bulk of security provisions almost entirely in European hands short of a full-blown ‘crisis’. This is more necessary than ever now, they claim, because China is the principal threat and the US does not have sufficient military resources to go round. The issue, as it was during the Cold War, is that it remains unclear whether the Europeans are willing or able to step forward to fill the gap.

There are signs that Europe is starting to wake up. Thanks in part to Trump’s pressure during his first term and, more significantly, due to Russia’s full-scale invasion of Ukraine, 23 of the 31 non-US NATO members are on track to meet the alliance’s two per cent of GDP target for defence spending. Poland has gone even further, spending four per cent of GDP and with plans to reach five per cent in 2025. But as Polish Prime Minister Donald Tusk put it, much more is going to be required of the entire continent. ‘Some claim that the future of Europe depends on the American elections,’ Tusk suggested, but in reality ‘it depends first and foremost on us… whatever the outcome, the era of geopolitical outsourcing is over.’ Similar sentiments were voiced on the other side of the continent by Benjamin Haddad, France’s Europe Minister, who maintained that ‘we cannot leave the security of Europe in the hands of voters in Wisconsin every four years’. It is time, Haddad declared, to ‘break out of collective denial: Europeans must take their destiny into their own hands’.