Why is it taking President Obama so long to decide what to do in Afghanistan? There are a lot of reasons, a few good, but most are the consequence of past mistakes.

The first is the sheer amount of information pouring into the White House, from the State Department, the Pentagon and Afghanistan. It is beyond the ability of any single person to read it all, said one who is witness to the flood.

That is a result not just of the deteriorating situation — as General Stanley McChrystal described it in his analysis — but of the White House having paid too little attention before Mr Obama gave his supposedly definitive statement of strategy in the spring. That was based on an analysis by Bruce Riedel, a former CIA officer, but lacked detailed knowledge of conditions on the ground and was more of a compilation of different views than a tight argument.

A second inhibition is the “2009 problem”: the US has more than doubled troop numbers this year but has little to show for it. That has held Mr Obama back from embracing General McChrystal’s call for 40,000 more troops. Many advisers support General McChrystal’s plan to train tens of thousands more Afghan police and soldiers as the only plausible way towards an exit.

But they are sceptical that the training can be accelerated as General McChrystal maintains. That doubt is supported by one policeman’s lethal attack on British soldiers this week.

Two US reports on training in September painted a bleak picture of the quality of Afghan recruits despite the $19 billion the US has spent since 2001.

The elections also proved a paralysing catastrophe. They left President Karzai as the winner, perched atop a Government whose nationwide reputation for fraud was only enhanced by its conduct of the polls. The US also needs to decide what to do with a collection of warlords and local powerbrokers whom it has paid to hunt the Taleban and Osama bin Laden, but who are widely resented.

British politicians and officers have told the White House increasingly directly that public support is falling while the President mulls over what to do. But although Americans’ support for the war is falling too, the anger, grief and open challenge to the strategy have not reached the levels in Britain. “We need time to get this right,” will be the theme of Mr Obama’s announcement.

His aides have agreed on one point: there is no “right” answer. They are trying to craft options for him, to “give him some space” to amend his policy again, when he finally does decide what it is.

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