There’s a reason they are not calling this Nato meeting a "summit".
Frankly, the last thing they want is a full-on, navel-gazing discussion of the alliance and where it is currently at, because the risk is that would simply turn into a very public row.
The official line is the alliance is in pretty good shape, and there is some truth in this.
Defence spending is going up, with nine countries now meeting the target of spending two per cent of GDP on defence - up from just four a few years ago - with others on course to do so by the target date of 2024.
Nato forces are deployed on the eastern frontier, technical co-operation between members is developing fast, and there are significant moves into the realms of cyber and space defence.
So what’s the problem?
Well, it’s not the military stuff, but the politics.
Three alliance leaders are throwing their weight around in a way the press loves, but which makes diplomats cringe.
Let’s take them one at a time.
Donald Trump has never been a fan of Nato. He thinks the other 28 are freeloading, getting collective defence on the back of the US taxpayer. He’s not completely wrong, but threatening Germany with punitive trade tariffs if they don’t pay more - as he did yesterday - is the surest way to tear Nato apart.
Emmanuel Macron recognises the threat that US disengagement could pose to European defence, and is determined to get the other leaders the think about it. Hence his comment that Nato is "brain dead".
The rest of Europe, however, would much prefer to wait and see if Trump is beaten in November 2020 allowing things to get back to "normal".
We’ll see who’s right, but if Trump wins a second term, Macron may get a much more sympathetic hearing.
It’s sometimes hard to remember that Turkey is member of Nato, given its forces have been challenging US troops in Syria, and it has just invested in a Russian air defence system rather than buying from the US or Europe.
This, to say the least, is not going down well.
France, in particular, seems determined to challenge Turkey’s President Erdogan on both these issues. Having all these rows in public, however, is not improving what is meant to be a celebratory birthday gathering.
Unless, of course, you are watching from Moscow.