By Jonathan Marcus
BBC diplomatic correspondent, Strasbourg
America remains the main source of Nato combat troops in Afghanistan
Afghanistan was what this summit was all about. As US President Barack Obama put it, "matching real resources to goals".
How real some of the commitments made here in Strasbourg really are will only emerge in time but Mr Obama himself seems to have gone away well-pleased with what has been achieved.
The predicted row between Europeans and Americans over the despatch of additional combat troops to Afghanistan never materialised.
This was in part due to skilful pre-summit diplomacy by the Americans but there was also a re-assessment of entrenched positions on all sides.
Washington came to the conclusion that persuasion would do more to extract additional commitments than blunt political force.
Washington also appeared to accept that it would ultimately have to do the bulk of the heavy military lifting itself.
That is what is actually happening on the ground in Afghanistan where the overwhelming majority of new combat troops will be American.
But this leaves all sorts of additional roles that can be performed by others.
More military training teams are urgently needed, more combat troops are required for the crucial pre-election period in Afghanistan and more money - lots more money - is needed to fund the expansion and improvement of the country's security forces.
On all counts there has been progress.
Making the case for the Afghan war at home is still a problem for many Nato governments - pressure from the Americans is not going to let up even if Washington's positions are couched in an accent more acceptable to European ears
The reason for the smiles - the Obama effect. The new US president has enthused, galvanised and re-invigorated Nato at one and the same time.
He has spoken the kind of language Nato countries have been wanting to hear from Washington for several years.
But US officials will be hoping that Europe was listening carefully to the president's message of renewal, for there was steel at its core - a determination that if the US is changing, then Nato allies have to change too.
They, the president made clear, must shoulder more of the burden.
Only one issue threatened to shatter the summit consensus - the selection of a new secretary general to lead Nato once Jaap de Hoop Scheffer stands down at the end of July.
Everyone - well, everyone, that is, except Turkey - wanted the current Danish Prime Minister, Anders Fogh Rasmussen, to have the job.
Turkey insisted "no".
The Turkish authorities are angry at Denmark for its failure to curtail the broadcasts of a pro-Kurdish television channel from its soil.
They are also not happy with Mr Rasmussen's behaviour during the "cartoons controversy" when a Danish newspaper published illustrations that inflamed passions in much of the Muslim world.
Role for Turkey
Efforts to resolve the diplomatic stalemate took up much of the summit's time.
There was a bizarre moment when Italian Prime Minister Silvio Berlusconi took a lengthy telephone call on his mobile, just as he was arriving to be greeted by the German Chancellor Angela Merkl.
This diplomatic faux pas is now explained as an element in the process that led to a deal. It was the Turkish Prime Minister, Recep Tayyip Erdogan, at the other end of the line.
Finally, after a face-to-face meeting between Mr Rasmussen and Turkish President Abdullah Gul and a significant push from Mr Obama, the Turks gave way.
But it looks as though they have won a significant package of inducements.
Sources close to the Turkish delegation say that Turkey will secure not just the post of Nato assistant secretary general but also that of the alliance's new civilian envoy to Afghanistan.
The key role of the US president is interesting here.
He is eager to reach out to the Muslim world, and Turkey's enhanced role in Nato is clearly intended as part of that effort.
All in all, then, a positive birthday summit for Nato but there should be no illusions.
Making the case for the Afghan war at home is still a problem for many Nato governments.
Pressure from the Americans is not going to let up even if Washington's positions are couched in an accent more acceptable to European ears.