Posted by 
At a recent election rally in South Carolina, Donald Trump said he would “encourage” aggressors such as Russia “to do whatever the hell they want” to Nato allies he considers to have not met their financial obligations.
Trump’s comments, however offensive, may merely be an electoral strategy. Why should, say, a South Carolinian citizen see their taxes go towards defending faraway lands, especially if they believe these partners are not willing to pay equally?
But there’s also a logic to his remarks that Europe should recognise, especially in light of Russia’s war in Ukraine. Many European nations need to build up their own security capacities again after years of lax spending on defence.
Regardless, such public comments from a presidential candidate have long been unthinkable. Since the second world war, America has sought out allies. What would it mean for the nation’s security, as well as that of the wider world, should they forego them?
British precedent
The modern US-led global order is in many ways a modern iteration of something developed by Great Britain at the beginning of the 19th century. Britain used the peace negotiations that followed the Napoleonic wars (1803–1815) to try and limit the power of expansive land empires like that of defeated France.
The 19th century is sometimes referred to as “Pax Britannica” (British peace) because of the relative absence of conflict between major European powers, with the notable exception of the Crimean War (1853–1856). It lasted until a unified German state emerged as a land power in continental Europe in 1871, upending the security presumptions of the post-Napoleonic peace.
One of Britain’s key reasons for fighting two world wars against Germany was to maintain its version of a global order. But, in winning, Britain depleted its finances – and capacity to maintain an empire – through borrowing from the US.
The US had become the new economic heavyweight, with a military built up and spread by wartime necessity. Its adherence to basic principles meant the British did not resist America’s newfound global primacy.
Free trade was to remain sacrosanct. Sea trade routes were defended as these were (and still are) vital for US economic superiority. The US would also maintain the kind of alliances that the British tended to turn to during times of war, where coalitions of allies share the costs and persevere towards victory.
Read more: With airstrikes on Houthi rebels, are the US and UK playing fast and loose with international law?
Lonely at the top?
The US would actively shape the world to its own liking in the post-war period. After the hyper-nationalistic conquests that were characteristic of its enemies in the first and second world wars, the US wanted no more empires.
It set up institutions dedicated to spurring free trade and global stability like the UN, the International Monetary Fund and the World Bank. And it formed alliances, most notably Nato, which included befriending wartime enemies like Germany and committing themselves to a long-term global role.
These alliances allowed the US to station troops overseas in strategic positions without having to administer a costly and potentially discontented empire, like the British and basically every world power had done before them.
Much of this was motivated by the Cold War. The Soviets had exchanged Nazi occupation of eastern Europe for their own. And it was widely believed that in the absence of US security guarantees, western Europe would also be invaded and made communist – an ideology that the US considered incompatible with its own.
The great power competition soon led to US involvement in other zones of communist activity, such as Asia. This was a period in which the US intervened in foreign governments and carried out or supported ethically questionable conflicts. For US politicians, however, it was generally bipartisan to believe that US intervention was justified by a bigger conflict between democracy and authoritarianism.
US power was also different to, say, the heyday of the Spanish empire in the 16th century. This empire did an excellent job of antagonising other powers and depleting its own vast resources in endless wars over honour and Catholicism.
Although certainly not universally loved, US power is not completely resented. This has much to do with America’s globally exported culture, from Hollywood to hip-hop. But also in how its power can be articulated as mutually beneficial to other nations, both in terms of trade and security.
We do not live in a peaceful world. But it is widely acknowledged that the world would become more dangerous if the US were to suddenly disengage. US security guarantees, for instance, disincentivise allies like Germany and Japan from developing nuclear weapons for their own safety.
Global security is American security
Supporting US allies, which was once a bipartisan issue in American politics, is becoming a zero-sum game – even though it is just about the most dangerous issue to do this with.
Bringing global security guarantees into question is exactly what states hostile to the US want. They know it weakens a world order that protects democracies, global trade, and weaker states that could otherwise be imposed upon militarily.
The US protects these not merely as an act of charity, but also because they are in the vital interests of America’s own safety, even if it can seem indirect to some American voters or the politicians who recently held up aid for Ukraine.
Ironically, a worldview that sees raw, almost mercantilist, selfishness as the entirety of foreign policy is exactly the thing that the US’s global order of free trade and respecting national sovereignty has discouraged for almost a century.
If America First becomes America Only, it might be a world view that certain regimes wish to emulate. But morally, it will not do what the nation managed in the past. To convert souls to an American future.
William Rees receives funding from The University of Exeter and The Royal Historical Society.
