The decision to call a second round of elections in Afghanistan, reluctantly accepted by President Hamid Karzai, was all but inevitable once it was clear the first round was seriously flawed by ballot-rigging. But it is still a high-risk strategy, and a huge logistical challenge, in the effort to produce a central government that will be seen as legitimate both inside and outside the country.

There are three main dangers to the exercise. First, the country could further solidify into polarised ethnic blocs, with the Pashtuns in the south and east backing Mr Karzai, while the Tajiks and their allies in the north back his principal opponent, Abdullah Abdullah, former foreign minister.