More than a 100,000 American soldiers were killed in the Second World War in Europe.From D-Day to Remagen to Bastogne, and on through Germany those soldiers were an essential part of the drive to rid Europe of Nazism.

Although Hitler had declared war on the USA in the aftermath of Pearl Harbor, US forces had largely been engaged against the Japanese. It had been the Imperial Japanese navy that had attacked American soil, not the Germans, but President Roosevelt decided the priority was winning the war on the faraway continent of Europe.

He could easily have simply concentrated on Japan first but took a strategic decision that went beyond simply looking at America’s own interest.

That sense of international action continued after the war as the US Marshall Aid programmes helped western Europe back onto its feet.

Britain was on its knees with so many dead, infrastructure destroyed and a brutal winter in 1947 preventing coal being moved to the power stations. It was American money that helped with the recovery.

The US also took Europe’s security seriously with the establishment of NATO.

Protecting allies was strong element of US policy until 2016 and despite complaints that other NATO members weren’t contributing enough to their own defence, that commitment never wavered. America was a dependable ally.

President Biden has continued that tradition. He is steeped in foreign policy expertise and understands the importance of NATO and the security umbrella over western Europe is as relevant now as it has ever been.

The knowledge that friends must look after each other has been a crucial element of strategic thinking since 1945, originally in response to a perceived Soviet threat.

Yet we still must ask if that commitment is as robust as it was, and what the implications are for Europe. The reason for that is simple - Donald Trump.

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No previous Republican president from Eisenhower to Reagan to Bush would recognise the current party. It looks more like a weird personality cult where the Supreme Leader is always right.

He is not allowed to lose elections and if he does then truth-free reasons have to be invented to create a narrative that he won.

The latest involves an allegation that Italians manipulated America’s voting system via satellites. Yes, really.

On top of that the party has moved in an authoritarian direction, openly promoting schemes to prevent their opponents voting and allowing states to simply ignore democratic elections if the wrong candidate is deemed to have won.

This is all based on a policy of “America First”; the idea that nobody and nothing else counts except Donald Trump’s interest, dressed up as “the national interest”.

Fundamental to that principle is the shabby treatment of allies such as Germany while cosying up to authoritarian strongmen.

Trump is even said to have threatened to pull out of NATO altogether.

It’s doubtful whether NATO’s fundamental principle of ‘an attack on one is an attack on all’ would have been respected if such an incident had occurred during his tenure.

Trump and his ideas haven’t disappeared; he might run again in 2024 or a younger mini-me might do so, using nationalist ideas and a compromised electoral system to snatch the presidency.

A new candidate might conceivably be worse, calling for the withdrawal of all US troops from overseas bases, heralding a new era of isolationism last seen in the 1930s.

Removing troops from danger on foreign soil is an attractive message even if past experience has shown that you cannot ignore security threats, they will catch up with you eventually.

The isolationism that gripped the US from the Treaty of Versailles ended up destroyed by the attack at Pearl Harbor.

Europe can no longer take the US for granted in the long term. All of NATO’s countries need to contribute an equitable amount of money to their own defence rather than over-rely on the US umbrella.

The UK is central to this with its larger than usual defence forces for a country of its size.

There will be some who will call on the UK to pursue an independent defence policy, even though that has never happened in the past and the UK is too small to be some kind of major player on the world stage. It needs allies and friends just like everybody else.

We can hope that Biden represents a new phase in American politics where the US is again a reliable and friendly ally, but we cannot take for granted the shield that the US has provided for 70 years.

A future administration might not see Europe as important, and choose to concentrate on the Pacific instead, looking to counter the influence of China.

Biden’s election is a time to breathe after the tantrums of Trump, but when it comes to Europe’s security, it certainly isn’t time to rest.

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