You don't need to be a student of the crushing of the Prague Spring in 1968 to find the sight of Russian tanks rolling into a neighbouring country chilling. The Georgian crisis is about more than vital issues of humanitarian need and rule of law over rule of force. It raises a fundamental issue of whether, and if so how, Russia can play a full and legitimate part in a rules-based international political system, exercising its rights but respecting those of others.

The immediate issues are clear. The ceasefire must be fully implemented. We need to see evidence that Moscow has now ordered Russian forces to withdraw to pre-August 7 positions and that this is happening.

Russian mind games on withdrawal do them no credit. The quick deployment of international monitors is also vital (the UK will play its full part in this). Humanitarian aid needs to be delivered quickly - again the UK is already committed in this area.

These actions need to be taken in the context of a clear diagnosis of the events of the last two weeks. For me, the fog of war does not obscure the basic points.

Since the early 1990s the frozen conflicts of South Ossetia and Abkhazia have been the subject of international mediation aimed at peaceful resolution. In the first week of August South Ossetian provocation prompted a Georgian military response. This then provided a pretext for overwhelming Russian aggression in and beyond the borders of South Ossetia. Russian forces also entered the rest of Georgia from Abkhazia.

Russia has provided no evidence of war crimes. If there is such evidence it must be produced, investigated and acted on. But Russian actions are untenable. First, in its own military operations, Russia has violated successive UN Security Council resolutions which they themselves agreed. Most recently Resolution 1808, passed in April, reaffirmed Georgian sovereignty and territorial integrity as well as limits on the Russian peacekeepers.

Secondly, Russia has, in the contrasting cases of Chechnya and Zimbabwe, argued vigorously against what it sees as international “interference” in internal affairs of sovereign countries. In this case it has blatantly violated the sovereignty of a neighbouring (and democratic) country. China and the Non-Aligned Movement will be surprised by this new position.

The British position is that aggression cannot and will not redraw the map of Russia's former “near abroad” (or anywhere else). The territorial integrity of Georgia must be respected. Democratically elected governments should be changed only by the people in free and fair elections. International law must be obeyed. This goes to the heart of the question of how Russia comes to terms with its past, and how it sees its future; above all, whether it recognises that the old frontiers of the Soviet Union are now history, and whether Russia sees its future as part of a rules-based international system.

The collapse of the Soviet Union created new facts on the ground - notably sovereign, independent countries with minds of their own and rights to defend. Many have already joined the EU and Nato; Ukraine and Georgia have said they want to and Nato has said that they can. This must be a choice for them. So in the EU and Nato, and through UN resolutions, we must strengthen our support for these countries, while at the same time organising our engagement with Russia to demonstrate the costs of adventurism and aggression.

At the emergency Nato foreign ministers meeting today I will argue for political and practical support for Georgia. Politically we need to reassert our commitment to its territorial integrity and, like the EU last week, to immediate international engagement with the long-term settlement of the frozen conflicts. Practically we need to confirm the commitment made at the Nato summit in April to membership for Ukraine and Georgia and to follow it up with serious co-operation - militarily and politically - as part of a structured route map to eventual membership.

Georgia and Ukraine are undergoing significant processes of reform. We should be seeking to support them as they develop themselves economically and politically.

In respect of Russia, I favour hard-headed engagement that leverages the benefits that the Kremlin needs from the international system - economically and politically - into a force for responsible behaviour from Russia.

We have significant shared interests with Russia, whether on energy, trade or stopping Iran from developing a nuclear bomb. And with a declining population and an economy not much bigger than Spain's, Russia needs positive international partnerships.

Our response should be to welcome them into systems such as the World Trade Organisation - if they are willing to abide by the rules. We should forge greater European unity on issues such as energy, and then engage with Russia: together we are Russia's energy market, and while it is a dominant supplier negotiating with 27 separate countries, it is far less powerful in the face of a concerted European negotiating position.

On the international stage, the UK favours reform of the G8 - notably expanding its membership to reflect the modern realities of the economic balance of power, and the position of countries such as India and China. I do not support Russia's expulsion from the G8: that would encourage Russian sense of victimhood, fuel Russian revanchism, and allow the Russians to position themselves as the champion of reform for those currently outside the G8. Instead we should use the G8 to work on issues where Russia can be a partner - whether on climate change or nuclear decommissioning. But we should also be prepared to act as a G7 when Russia acts in flagrant breach of international law and flouts our values.

Russian wedge-driving, across the Atlantic or within Europe, will not work if we stick to these principles and apply them properly.

The Russian Foreign Minister said last week that there were no winners from the conflict. That must indeed be the outcome.

- David Miliband is the Foreign Secretary

Times Recommends

• A dose of defeat is just the medicine
• Protecting ourselves from Eurocreep
• After the summer of LUV, it'll still hurt