The 122 veterans, whose service spans the period from the Second World War to modern-day conflicts in Iraq and Afghanistan, said that the peace which has prevailed in Europe since 1945 “should not be taken for granted”.
The letter came as D-Day veteran Eric Chardin, who was 19 when he took part in the 1944 landings, said that the prospect of Brexit worried him.
“I can’t help feeling that it would be an awful shame if what we’ve gone to so much trouble to do, to collect the European big nations together, to break it all up now would be a crying shame,” said Mr Chardin, 94, from Cambridge, in a BBC interview at the 75th anniversary commemorations in Portsmouth.
Issuing a call for a Final Say referendum on Brexit, the signatories to the letter - published in The Independent - said that the EU should take credit for helping keep the peace in Europe.
And they challenged the invocation of wartime patriotism by the Leave camp, pointing out that it was Sir Winston Churchill who called for the creation of a “European family” to prevent another descent into bloodshed.
Churchill’s words helped inspire the creation of the Common Market, which evolved into the European Union with “one main purpose - to create lasting peace by entwining our economies and societies together on a continent once ravaged by war,” they said.
“Nato does not keep the peace in Europe – it keeps peace for Europe. It is the EU that keeps peace in Europe, because when you trade, you do not fight.
“As former members of the armed forces and veterans of more recent conflicts, we have served alongside soldiers from other European nations, supporting each other while under fire or facing danger.
“We have learnt that war stinks, that peace is the natural goal for civilisation, and that Europeans are our brothers in arms.
“But that peace and friendship is now threatened by Brexit. Peace in Europe is not something that should be taken for granted
“We should be proud to lead in Europe, proud that our friends respect us and can rely on us. That’s why we, as former members of the armed forces, all support a People’s Vote on Brexit.”
Signatories include veterans of the Royal Navy, RAF and Army, including Brigadier Stephen Goodall, who saw action in Burma during WW2, as well as the co-founders of Veterans for Europe Stuart Thomson, Duncan Hodgkins and Steve Gavin.
Gulf War RAF veteran Corporal Thomson, from Worcestershire, said: “On D-Day, 75 ago, our brave forbears went over the Channel to help our friends who had been under oppression for almost five years.
"We went there to help the French, Belgians, Dutch, Norwegians, Danes, and even Germans who were oppressed by the Nazis. Thirteen nations, including British, Irish, French and Dutch, also Belgians, Poles and Czechs - from all branches of the services - were part of that liberation coalition.
“As Europeans, we were stronger together then and should be stronger together now.”
He added: “What has happened since 2016 is very disturbing, and it’s clear that the military aspects of Brexit weren’t thought about properly.
“Politicians trying to force us out of the EU without going back to the people are cowards, not leaders. They have no mandate and no right to behave this way. Those of us who fought for democracy are demanding a democratic People’s Vote to hold them to account.”
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