The French city of Strasbourg and the German town of Kehl, which face each other across the river Rhine, will be in lockdown this weekend.
The grandees of Nato (the North Atlantic Treaty Organisation) are gathering to celebrate the alliance's 60th anniversary and protesters are homing in on the site from all over Europe.
It will be quite a party if you have the right security passes, for Nato is undeniably the most successful alliance in history.
It's almost 20 years since the original reason for Nato's creation, the Soviet Union, disappeared, but there is still a queue of countries clamouring to join.
Croatia and Albania will become Nato's 27th and 28th members at this summit, and there are half a dozen more countries waiting at the gates.
Yet behind the festivities, there are two major problems that the alliance needs to confront at this summit. The one that gets all the public attention is the stalemated war in Afghanistan.
Afghanistan has been a problem for the alliance from the start, for some members were much keener on the adventure than others. About half of the foreign troops in Afghanistan are Europeans and Canadians who operate under Nato command, and they have taken almost as many casualties there as the US troops - but their losses have been very unequally shared.
Only three countries with a total population of under 100 million people - Britain, Canada and Denmark - have suffered almost two-thirds of all Nato's fatal casualties in Afghanistan.
France, Germany, Italy, Spain and Poland (total population 280 million) have altogether lost fewer soldiers than Canada alone. (Canada's population is 33 million, but it has lost 116 soldiers in Afghanistan.)
As you would expect, this disparity generates some bitterness in the ranks of the alliance. But the "shirkers" don't feel any need to apologise: they are hanging back from the fray mainly because they don't think it's worth getting their soldiers killed for.
They can't say that in public without breaking alliance solidarity, so they have to bear the media accusations of cowardice in silence.
But if they privately think (as they do) that the war in Afghanistan is neither necessary nor winnable, why would they agree to get a lot of their soldiers killed there?
President Obama's "new strategy" for Afghanistan, which will be presented at the summit, will not change any minds, for it is too obviously just the old Bush strategy repackaged. And the supporters of the Afghanistan war who warn that it is a make-or-break test for Nato are just trying to bully the less enthusiastic alliance members into doing more - it's not really important enough to threaten Nato's future in any way.
Sooner or later Western troops will leave Afghanistan, having failed to "fix" a country that is very resistant to foreign meddling. Nothing especially bad will happen elsewhere because of this failure, and the whole episode will quickly be forgotten.
The real threat to Nato's future lies elsewhere. Since the Cold War ended 20 years ago, every former Eastern European satellite of the old Soviet Union has joined Nato, including the three westernmost republics of the Soviet Union itself (Estonia, Latvia and Lithuania).
This has caused much distress in Moscow, which thought Nato had promised not to expand into Eastern Europe if it freed the satellites. But the promise was never put on paper, and the Russians have taken Nato's expansion reasonably well in the circumstances.
Now, however, Nato has promised to admit Ukraine and Georgia, two former Soviet republics that lie not west of Russia, but south of it. The old fear of "encirclement" has revived in Moscow, and the Russians warn that relations will get very frosty indeed if Nato expands into these countries.
There is little enthusiasm for this expansion among the older members of Nato in Western Europe, and not much in Ukraine either - only about one-fifth of the Ukrainian population wants to join Nato, although the Government is keen.
Nato membership is wildly popular in Georgia, but for the wrong reason: President Mikheil Saakashvili's Government stupidly tried to seize the breakaway province of South Ossetia last summer, killing Russian peacekeeping troops in the process, and then rapidly lost the ensuing war with Russia.
There is strong support for Ukrainian and Georgian membership in Washington and among the new Nato members in Eastern Europe, and so far the Western Europeans have reluctantly gone along with it. Next year's Nato summit may well see both countries admitted to membership - but that would ultimately destroy Nato.
The alliance was founded on a guarantee that all members would come to the aid of any member that came under foreign attack. It was a believable guarantee, and therefore a strong deterrent to any attack; whereas nobody in their right minds believes that Nato would risk fighting a nuclear war with Russia to save Ukraine or Georgia if they should stumble into a military conflict with Moscow.
So if Nato lets those countries in, it will become a two-tier alliance, with real guarantees for most members and paper promises for the others.
In due course, doubts will arise about whether all the Eastern European members are really covered by the alliance guarantee either. And if that happens, Nato finally dies.
* Gwynne Dyer is an independent journalist based in London.
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