What does Nato hope to achieve?
The Nato summit in Lisbon has an impressive sounding agenda but it will have to deliver if it wants the meeting to be more than an expression of intentions.
The summit, which begins on Friday, will launch a new so-called "strategic concept", formally agree on the start next year of a hand-over of leadership of operations against the Taliban in Afghanistan to Afghan forces, and try to repair the relationship with Russia by agreeing to study an anti-missile system and drawing up a list of common threats.
The Strategic Concept
Nato regularly examines its role and last did so in 1999.
The best summary of the result this time was probably given earlier this week by the Nato secretary general himself, Anders Fogh Rasmussen.
"I would describe it as territorial defence in a modern world. Nato's core function is still territorial defence of our populations and our member states," he said.
"However, we have to realise that in today's security environment it may on occasions be necessary to go beyond our borders to protect our people effectively. And of course, Afghanistan is a case in point."
What this means is that Nato will go on intervening around the world where it feels the joint security of its member states is at risk. Not so much a new concept therefore as a continuation of the old.
One new element will be a plan to reduce the numbers of Nato personnel, command structures and agencies.
The summit is expected to formally agree (with President Karzai there) a timetable under which a transition to Afghan military leadership against the Taliban will start next year with a view to completion in 2014.
The commitment is important for US President Barack Obama as he begins to plan his campaign for a second term and for British Prime Minister David Cameron.
Mr Cameron said this week: "I have said that our combat forces will be out of Afghanistan by 2015. And this week's Nato Summit in Lisbon is set to mark the starting point for passing responsibility for security progressively to Afghan forces."
However, a timetable for a Nato withdrawal from a combat role is likely to produce problems if there are not sufficient results on the ground.
What happens if the Afghan forces prove incapable of taking over?
There has been a thaw in Russian thinking towards the West over recent months under President Dmitry Medvedev's policy of economic modernisation.
The president will be in Lisbon for the first meeting with Nato leaders since the Russian action against Georgia in 2008.
End Quote Anders Fogh Rasmussen Nato secretary general
I think we are witnessing a fresh start in the relationship between Nato and Russia”
Russia seems ready to help the Nato operations in Afghanistan, where it wants stability, by easing the transit of non-lethal cargoes (including armoured vehicles) in both directions.
It is also likely to provide 20 transport helicopters to the Afghan government and the training to use them.
The big idea in Lisbon is to agree on a Nato-Russian joint study of missile defence.
This was once the issue that divided them most, but following President Obama's cancellation of the proposed anti-missile system in Poland and the Czech republic, it is now the means to potentially bring them together.
There would not be a common system but co-operation by both sides.
Mr Rasmussen has high hopes.
"I think we are witnessing a fresh start in the relationship between Nato and Russia. And maybe I could go further and say a fresh start in the relationship between Russia and the West.
"And I think this is of huge strategic importance. To my mind the future of Russia lies within positive co-operation with the European Union and Nato."
Nato and Russia might find common ground in agreeing on a list of threats to them both - from missile development in a number of countries (Iran is unlikely to be singled out) and cyber warfare, for example.
The Russians are cautious. The Russian ambassador to Nato, Dmitry Rogozin, has said that Moscow would have to be sure this did not threaten Russian's strategic missile potential.
Such talk of missiles still worries Russia's closest neighbours and is another sign that a fundamental improvement in relations with Russia instead of a lowering of tensions has yet to take place.