It was impossible not to be moved by the dignity of the diminishing band of D-day veterans in Normandy, 75 years after “the longest day” led to the opening of a new western front that helped bring about Adolf Hitler’s downfall.

Men like Kenneth Hay, who read a poem, Normandy, by another veteran, Cyril Crain, to the congregation at Bayeux Cathedral. As he spoke its concluding words, “When my life is over and I reach the other side, I’ll meet my friends from Normandy and shake their hands with pride”, his voice began to break.

Even organising the acts of remembrance in the UK and France was described by the Ministry of Defence as “one of the biggest mobilisations of UK armed forces in recent years”, involving 4,000 service personnel in events ranging from parades to flypasts.

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The performative function of the modern military has arguably never been more important, at a time when British forces are by historical standards only lightly engaged overseas, a decade after combat operations ended in Iraq and five years after they ceased in Afghanistan.

It was intended, of course, to be symbolic of Britain’s first steps into its post-Brexit international order, showing that the UK is still able to act as a link between the US and continental Europe – and that the military can act as a bridge between fading memories of the past and the challenges of the future.

Even with the Brexit deadline missed, it was no surprise that Theresa May emphasised the UK’s ongoing commitment to Nato in her press conference with Donald Trump on Tuesday. Both the UK prime minister and US president agreed it was incumbent on other Nato partners to spend more on their armed forces.

It was also no surprise that so many world leaders came to Portsmouth, including the German chancellor, Angela Merkel- whose presence was lost on the former Republican governor Mike Huckabee – or that the French president, Emmanuel Macron, declared in Normandy: “The debates taking place today cannot affect the strength of our joint history and our shared future.”

Reflecting on the anniversary events and the veterans present, Gen Sir Nick Carter, the UK’s chief of the defence staff, said that “as D-day fades from living memory to legend we must listen, learn and continue to tell their stories for them”.

That is part of a long-established tradition of remembrance, but it has extra importance because of the growing unpopularity of military engagements, with both the public and parliament reluctant to support the deployment of troops or risk civilian lives.

Polling conducted by YouGov last month (pdf) found that 83% of Britons believe UK military involvement in the second world war was justified. Only a minority, however, endorse the wars of the past three decades in the Gulf, the Balkans and Afghanistan. Support for the 2003 invasion of Iraq is as low as 19%.

The curiosity is that even in D-day week the military thinks the days of “missiles and tanks” are largely over. In a speech earlier this week, Gen Sir Mark Carleton-Smith, the chief of general staff, even said peace and war were “two increasingly redundant states”.

In a clear reference to Russia and perhaps China, Carleton-Smith said authoritarian regimes were “exploiting the hybrid space that exists in between” – disinformation, subversion or cyber – where lives may not immediately be at stake but economies, livelihoods and ways of thinking are.

It may be ironic to reflect that amid the D-day showpiece and its contribution to our sense of nation, the recollection of its human cost has already been an effective deterrent to future wars of its kind.

And that as the military seeks to draw strength from the past, the terrain in which it operates today is radically different to the beaches of 75 years ago.