Peace: the single most important reason for the creation of what we now call the European Union, and the reason it remains so crucial. The European project arose from a clear vision: to make war in Europe ‘materially impossible’, to create enduring peace in a continent long ravaged by war. It is almost impossible to imagine now the devastation that plagued our continent for so long. And that is thanks to the visionary ideas of its founders. A spirit of reconciliation and mutual cooperation among the six founding members was crucial to ensuring Immanuel Kant’s idea of perpetual peace seemed to be a reality.

Of course, many would argue that is NATO that has kept the peace in Europe. It has certainly been important in securing the borders of its European members. During the Cold War the European Community as it was initially known could rely on an American security blanket to protect them from Soviet threats. Yet, within its own borders it was the mutual trust that developed as a result of pooling sovereignty in the areas of coal and steel and then across a wider set of economic policies that ensured member states began to see each other as partners and allies, not potential invaders.

For generations now we have lived secure in the knowledge that our fathers, brothers and sons will not be summoned to fight for our country. Military engagement by the state and by individuals signing up is voluntary, not forced. We have the EU to thank for that.

And it is important to remember that this is a voluntary union, not a forced marriage. Yes, there is a degree of negotiation and compromise involve as happens in any relationship. Ultimately, the UK can decide what role it plays in the EU; it isn’t coerced into action. In the 43 years since the UK joined we have seen our influence wax and wane, mostly dependent on how engaged the government of the day has sought to be.

At times we have led, as in the initiative to ‘complete the internal market’ enshrined in the Single European Act (SEA). Taking down internal barriers to trade, including free movement of goods, capital, services and labour – envisaged in the founding treaties but taken so much further in the 1992 programme – was pushed by Margaret Thatcher, and it achieved a huge amount. When the UK engages we can make a significant difference to the EU, to our mutual benefit; when it takes itself to the side-lines its influence is inevitably reduced.

You don’t have to love all the details of the EU to believe that it has played a crucial role in the peaceful development of first six and now 28 member states, but you do need to be part of that Union to influence and improve it. Being part of the world’s greatest peace project remains a great prize.

This article is from the EuroFile (pdf)– a collection of essays offering a positive, liberal case for Europe

* Julie Smith is a Senior Lecturer in International Relations at the University of Cambridge, a member of the House of Lords and Cambridge City Council