The year 2025 will be looked back upon by future historians as the end of what was the ‘Atlanticist Era’. This, begun in 1941, was one in which the United States served as the global guarantor of the Atlantic Charter. The previous era, which started at the end of the Great War in November 1918, was one of increasingly belligerent isolationism across the US. This strand in the American national psyche is a strong one, and has received a new shot in the arm with the election of President Donald Trump. But it is by no means dominant. The US remains bound by ties to the world, ties built through blood and hardship since the Second World War that even Trump will find difficult to undo.

The Atlantic Charter was a remarkable and ground-breaking agreement, providing in words a commitment by the US and the United Kingdom to a new set of global security imperatives that would shape the world once German fascism had been defeated. These words, agreed by Franklin Delano Roosevelt and Winston Churchill in August 1941, ultimately condemned Britain to the loss of her empire.

The charter held that (1) neither nation sought any aggrandisement; (2) they desired no territorial changes without the free assent of the peoples concerned; (3) they respected every people’s right to choose its own form of government and wanted sovereign rights and self-government restored to those forcibly deprived of them; (4) they would try to promote equal access for all states to trade and to raw materials; (5) they hoped to promote worldwide collaboration so as to improve labour standards, drive economic progress, and enhance social security; (6) after the destruction of ‘Nazi tyranny’, they would look to build a peace under which all nations could live safely within their boundaries, without fear or want; (7) under such a peace the seas should be free; and (8) pending the establishment of a general security through the renunciation of force, potential aggressors must be disarmed.

Roosevelt signed the charter precisely because he considered it to be in the US’s national interest. He was surprised that Britain had survived three years in the ring with Nazi Germany, and his personal (though not political) view was that Britain should be given all support ‘short of war’. This was not merely because it meant that American businesses, in the years after the Great Depression, would thrive by becoming the ‘arsenal of democracy’. It was also because Roosevelt knew that global peace and a stable international security environment were good for the United States.

After the war, the Atlantic Charter became the basis for the United Nations. But remember that, although FDR signed the Atlantic Charter with Winston Churchill in August 1941 and energetically provided goods for Britain’s war effort, the real prompt for the US to put its money where its mouth was came with the Japanese attack on Pearl Harbor on 8 December 1941. Without the onset of war with America, the US would undoubtedly have remained uninvolved in the events in Europe, and the deeply ingrained isolationism of the majority would have triumphed over the internationalist sentiments of a minority.

These isolationist sentiments were remarkably strong. Indeed, in 1937 the United States had enacted the so-called Neutrality Acts, legalising America’s descent into isolation from political entanglements abroad – specifically in Europe – by making it difficult to trade with any warring country regardless of the righteousness of the cause. Some of these powerful impulses were built on fears that America had been hoodwinked into joining the fighting in Europe in 1917.

Contrary to popular belief, the end of the Second World War did not mean the beginning of Pax Americana. In the years between 1945 and 1949, the United States once again withdrew into itself, demilitarised, and expected to reestablish the domestic and international political structures that had existed in 1939.

In its naivety, the US had not reckoned with the USSR, which had been working assiduously since 1944 to build a postwar settlement that favoured Soviet interests. This had the perverse (and probably unintended) effect of slowly compelling reluctant Western governments to organise themselves into a defensive alliance. The Berlin Blockade in 1948-49 saw the arrival at British airfields of nuclear-armed American aircraft. For the first time in her history, Britain signed a treaty that created a binding, collective commitment to the continent of Europe, first with the Western European Union in 1948 and then with the North Atlantic Treaty Organisation (NATO) in April 1949. If this was a radical shift for the United Kingdom, in light of Britain’s historical reluctance to make long-term European commitments for her armed forces, then this was equally true for the United States, which had now decisively turned its back on the strident isolationism of 1919-49. That era had now passed into history. The United States Congress passed the Mutual Defence Aid Programme in a direct recognition of the Soviet threat. With the detonation of the first Soviet atomic bomb in August 1949, followed by the victory of Mao Zedong’s communist forces in China in October, Western fears did not seem at all exaggerated.

The big difference between 1939 and the present day is that, try as it might, the US will never be able to extricate itself fully from the ties that bind the West together into the collective security mechanisms established with great wisdom by our forefathers. They knew the scale and nature of the threats to national and global security. We have forgotten these, but this collective amnesia will be temporary.

One of the key elements in the post-1945 global security structure is the UN. The other is NATO. NATO was built on the collective premise that also lay at the heart of the UN, which itself had been created at the end of the war in October 1945. Where, to paraphrase Winston Churchill, ‘jaw, jaw’ failed, ‘war, war’ would be authorised against malefactors by the UN on the basis of six clauses in the United Nations Charter. These include Articles 42 and 43 of Chapter VII, which inter alia authorised the Security Council to ‘take such action by air, sea, or land forces as may be necessary to maintain or restore international peace and security’ and obliged all members ‘to make available… armed forces, assistance, and facilities, including rights of passage, necessary for maintaining international peace and security’. For a generation of men and women who were sick to death of the relentless wars that they had experienced in their lifetimes, the creation of the UN heralded an opportunity to embrace international peace. Crucially, this would be based on a new legal footing backed by the commitment of its members to act together rather than, as in the past, in isolation. Self-interest was being redefined as collective interest in pursuit of international stability and peace, through a new organisation that had learned from the weaknesses of its predecessor, the League of Nations.

This is the key issue for today. Isolationism is the natural, emotional impulse of men such as J.D. Vance, who have been brought up on concepts of American essentialism and who don’t understand that the world works (or doesn’t) as a system of states acting and cooperating together in unison. But true American isolationism will never be a reality unless the US also abrogates its commitments to the UN and NATO. I doubt that we’ll see that, at least in the short term. In the immediate term, we’ll see the US attempting to assert a domestic message that chimes with that of the America First of the late 1930s, without trying too hard to divest itself of all its internationalist encumbrances. Ukraine is the first victim of this attitude. Hopefully, a shocked Europe will step into the breach, though European disunity on security has long been a joke among those who understand it.

Ironically, however, it is these encumbrances – NATO and the UN – that give the US much of its power. The Atlanticist Era has made America Great in a way that it never was before the Second World War. There will be a lot of noise, even shouting, in the White House at men like the Ukrainian president who don’t bow low enough before the self-evident totem of American power. But it will end. The US is the world’s natural superpower, not because it is strong but because it is free. It’s just that Trump and Vance don’t realise this yet. In the long run, Atlanticism will be back.