Tom Tugendhat is the author of The Fog of Law, published by Policy Exchange. He was previously Military Assistant to the Chief of the Defence Staff and is Conservative PPC for Tonbridge and Malling.

Few alliances in history have been as successful as NATO. It has won a global war whilst avoiding global conflict; normalised peace in Western Europe so completely that many now wonder whether we need it at all; and helped bring once oppressed nations into the family of democracies.

These achievements have led to some unintended consequences. Germany, which understandably values pacifism above martial virtues, has slashed defence spending to its lowest level in generations. Italy, Spain and Portugal, countries whose economies have suffered dreadfully over the past few years, have prioritised welfare over protection. Even Poland, Hungary and Romania, nations who know that the real cost of an unguarded border is the envy of less happy peoples, are accepting greater risk and cutting back their Armed Forces Across Europe, uniforms seem incompatible with the golden peace we have enjoyed since the end of the Cold War.

That leaves the only four countries spending even the modest NATO target of 2 per cent of GDP. In effect, the US, Greece, Estonia and the UK are now carrying a disproportionate burden for our common security.

But this isn’t only about money. It is about how we see the world and how that, in turn, shapes our decisions. Until this summer, many of our allies could see no real, existential dangers, as even for Eastern Europe the threat of Russian militarily action was remote. Moscow could close down an economy, as they did to Estonia in 2007, and back armed separatists, as they did in Georgia in 2008, but the idea that Putin would seek to redraw borders was not credible.

Today that illusion is shattered with the annexation of Crimea, war in eastern Ukraine, and the march of the so-called Islamic State on the borders of Turkey. Putin even warned Barroso that he has nuclear options.

That means the settlement of the post-Cold War era is ending. Those who put the EU at the heart of Europe’s security structure are realising it isn’t geared to rapid decision-making and that NATO is now regaining importance. So the 28-member alliance is at a turning point. For the first time in a generation, NATO must not only standardise military equipment, training and command structures, it must remember its primary purpose: the defence of our values and interests as democratic, free societies.

This demands a renewal of the 28-member alliance. To ensure Britain shapes the debate, David Cameron was right to grasp the opportunity to host the NATO summit. No country is as well placed as Britain to argue for increased spending and a greater commitment to the network of intertwined allies and partners that makes up our alliance.

The issues for immediate discussion will start the debate but should not define it. Ukraine and Afghanistan must be addressed, to achieve a common approach to defending our allies and to end NATO’s longest expeditionary operation. but the conference at Celtic Manor in Newport should go further than that.

With 70 heads of state and government it will be hard to find common ground, but doing so would make the alliance, and Britain, stronger.

Today, NATO’s security threats are emerging from new directions: Turkey’s border is facing the so-called Islamic State whose barbarism is destroying communities and homes. NATO’s northern border sees Russia again replacing negotiation with aggression in trying to secure access to resources under the Arctic Sea. In both places, the alliance needs to reassure friends that we have the will to defend our interests and allies because, like all treaties, NATO’s strength relies on having the confidence that their agreements will be honoured.

NATO also needs to think of non-traditional threats, and what acts could trigger an Article 5 response. 60 years ago, the answer to this would have been simple  Soviet troops crossing into Norway or West Germany would have resulted in a united action. But today, when Russian government hackers close down an economy, or could potentially murder hundreds in hospitals and towns by disrupting electrical supplies, the answer is less obvious.

Can NATO respond militarily if the soldiers attacking them are in a tower block in Shanghai and are part of the Chinese Army’s Unit 61398, responsible for cyber warfare? Should NATO build a common cyber-defence policy to counter-attack enemy networks? The discussion is becoming more urgent.

That’s why the work of Tobias Ellwood, the Foreign Office minister, in preparing our allies and partners for these conversations, has been essential.

Allies and partners for peace, when they are willing to pull their weight, deter threats. That means expanding NATO’s clear command structures that allow others like Australia, the UAE and Japan to play a full role, reinforcing the need for all to understand why defence spending isn’t optional, and not undermining the alliance by creating EU parallels.

This is an ambitious aim for any conference, but with Russian tanks in Luhansk concentrating the attention of leaders worldwide there is a chance that all will realise we are at a tipping point. Get it right and NATO will ensure that the summer of peace we have enjoyed in most of Europe since the fall of the Iron Curtain continues. Get it wrong and the lessons Putin is teaching the world – that violence is unopposed and nationalist aggression can secure popular support for little cost – will become the example others follow.

In Newport, the future security of Britain and the democratic world is at a fork in the road. The questions Cameron has put on the table are the right ones, our allies must now play their part in answering them.