The world hardly noticed when its most powerful collective security organisation got a new secretary-general this week. It should. Nato may not seem as immediately relevant as when Soviet tanks were poised to race for the Rhine. But the job facing Anders Fogh Rasmussen, a former Danish prime minister, is crucial – and daunting.

Nato increasingly risks being seen as an optional alliance where countries pick and choose their obligations. The vast majority of troops in Afghanistan, where Mr Rasmussen is on Friday, are from a handful of members. Such asymmetry is not atypical. It rankles.