On this day in 1945, the guns fell silent across Europe. After six long years of war, the UK and its allies had finally defeated Nazism.

Out of the rubble of the Second World War, Europe began to rebuild. Millions of displaced people, imprisoned in Nazi labour camps or forced to flee as war destroyed their communities, returned home. Some built new lives in the countries that welcomed them in. Across the continent, governments and citizens vowed never again to allow this to happen.

It was this determination – to defend Europe from what Winston Churchill called “the two giant marauders” of war and tyranny – that heralded the birth of the European Union.

The EU was forged from an understanding, learned through the grim lessons of two world wars, that the interests of one nation cannot be separated from the interests of all. Europe is inextricably linked: our lives are intertwined.

As Jean Monnet, the French economist and influential supporter of European unity, once said: “better to fight around a table than on a battlefield”. Through EU membership, sovereign nations found a way to resolve their disagreements without resorting to war. The EU was a bold collective effort to enhance a mutual commitment to peace, freedom and human rights.

In the decades since, the EU has lived up to those ambitions. It has helped foster democracy and human rights in former Soviet Republics. It has aided reconciliation between the Balkan nations that were at war just two decades ago.

Its core principle of free movement has allowed people once divided by trenches or walls to live, work, study and raise families together across the continent. And Europe has never again experienced conflict on the scale of the Second World War.

For some, its success has bred complacency. As the memory of the Second World War grows more distant, many have begun to take peace in Europe for granted. But we must not be fooled into thinking that war is impossible, nor forget the importance of the EU in preserving that peace.

We need only look at Northern Ireland, where the EU has played an essential role in forging peace. Britain’s common membership of the EU has strengthened its relationship with Ireland immeasurably. The shared European identity of both British and Irish citizens has helped to heal divisions, and underpins the Good Friday Agreement.

The murder of Lyra McKee in Derry last month is a tragic reminder of how fragile that peace really is. Brexit is a clear threat to peace in Northern Ireland; the New IRA have already describing it as an “opportunity” to recruit young supporters and commit further acts of violence.

We owe so much to the generation who lived through two world wars, witnessed death and destruction, and made sacrifices to defend our country and our values. They possessed the vision, courage and resolve to build a new forum for peace: the European Union.

Instead of turning our backs on this endeavour, we must rededicate ourselves to the cause of peace in Europe – and to the EU as the best way of maintaining that peace.

That is why the Liberal Democrats are campaigning unequivocally to stop Brexit: to maintain the hard-won peace in Northern Ireland and across Europe, and to continue resolving our disputes in the halls of Brussels, rather than on the banks of the Somme, the beaches of Normandy, or the streets of Belfast.

Jo Swinson and Ed Davey are Liberal Democrat MPs for East Dunbartonshire and Kingston and Surbiton.