When asked about the future security of the United Kingdom those who wish to leave the European Union have a one-word, simple and simplistic answer – Nato. As if that was the end of the matter.

But in doing so they ignore the history of the European continent. Those who conceived of the creation of the European Coal and Steel Community in the aftermath of the Second World War did so in recognition of that history. Armaments had not brought peace or security to Europe, indeed the opposite. Their reasoning was that those are economically close are less likely to be at each other’s throats.

Coal and steel may now seem a modest beginning for the EU but the six countries which joined together were those who had suffered the greatest physical and social damage in the war.

They had a common interest in coal and steel, the necessary components of rebuilding the fabric of their countries and restoring their economies. Self-evidently and openly economic cooperation had the political purpose of fostering and maintaining stable and peaceful relations with each other. Britain's decision to join the Community had similar objectives.

With common political interests the expanding membership of the EU has been based on human rights and democratic values. Nor is it any wonder those European countries escaping from the pollution of fascism and communism have for reasons of both trade and security wanted to join the EU as well as Nato.

Their purpose in doing so is to provide a stable and lasting peace on which to build and maintain their new found commitment to democracy.

The Brexiters argue the EU wants to create an army for itself and that this would undermine Nato. But go round the capitals of the members of the States of the European Union and ask if their governments want an EU army. Apart from Mr Juncker, the President of the Commission, you will find very few takers.

The reason is that the continuing centrepiece of Nato is the American commitment to Europe. Faced with an increasingly assertive Russia why would any European government want to create a rival to the defence organisation which has at its heart the mighty US and has served the continent well.

But there is an issue where European members of Nato need to step up to the plate. And that is in defence expenditure.

The Nato obligation to spend annually 2 per cent of GDP agreed at Celtic Manor in 2014 is a minimum and only a handful of nations have achieved it. In the case of the United Kingdom creative accounting required the inclusion of armed forces pensions and expenditure on the security services to fulfil the obligation.

In Washington the administration and members of Congress are expressing their concern that Europe gets its defence on the cheap at the expense of the US. At the upcoming Nato summit in Warsaw in July you can be sure this issue will once again be on the agenda. And this time the exchanges may be even more frank.

A rebalancing by the US towards the East in response to China's increasing confidence inevitably has implications for resources and the pressure on Europe will grow and the language more strident.

So why are Nato and the EU together necessary guarantors of our security? There is an obvious answer. It is Mr Putin. His determination to make Russia more influential on the continent of Europe rests on two pillars.

First the destabilisation of the European Union and second the undermining of Nato. He talks of a "new security structure for Europe" with Nato diminished, the EU fractured and Russia dominant. There is still resentment in Russia that when the Warsaw Pact collapsed Nato did not go into voluntary liquidation.

Putin's support of dissidents in the Ukraine serves both his European objectives. Don't dare expand membership of Nato or the EU. And don't forget just how fragile the Baltic states are, with their Russian-speaking populations and Kaliningrad on their doorsteps.

The response to Russia's ambition has been two-fold. Unanimous EU-wide sanctions which have had a significant impact on the Russian economy and Nato's decision to deploy more forces in Eastern Europe to underline the Alliance's commitment to all of its members.

If you need any evidence that the EU and Nato are both necessary for the security of Europe this is plain for all to see.

Lord Ming Campbell is leader of the European Movement in the Scotland Remain campaign.