Now we know the plan for British troops in Iraq: begin to pull out, leaving a few thousand for training and helping with emergencies.

Des Browne, Defence Secretary, shaded in some of the blanks yesterday in what is now Britain’s exit strategy.

Some in the Bush Administration think that the US should emulate Britain’s tactics; others, that they risk more turmoil, and are a luxury available only to the junior partner in the coalition.

In Afghanistan, in contrast, Britain has taken the lead: of the Nato forces; of the anti-narcotics effort, and of the turbulent south of the country. It not only has no exit strategy, it is also trying to persuade others to enter.

It risks putting itself in Afghanistan in the same predicament that has engulfed the US in Iraq.

Yesterday Browne, over-chatty at being released on to recently forbidden territory, told Chatham House, the think-tank, that “I can tell you that by the end of next year I expect numbers of British forces in Iraq to be significantly lower — by a matter of thousands”.

The confiding tone was unnecessary; the taboo at discussing a pullout for Britain’s 7,000 troops was broken last week by Margaret Beckett, Foreign Secretary, who told the House of Commons that half could be home by the middle of next year. Browne’s revelation that “the planning for this has been going on for months” will not boost Government credibility, given how often ministers have denied planning for an imminent exit.

The plan is to leave some forces there for training and for protecting supply lines. Some will also stay as “quick response” teams, Browne said, “ready to support the Iraqis if the situation gets out of control”. That reassurance is rhetorical; Britain will be out in all but name. A few thousand troops are too few to stop even a rally getting out of control.

The US has accepted Britain’s tactics because it can see the cost to Tony Blair of the war; the plan tests the hazards on the route to the exit; and Britain has argued that it needs the troops in Afghanistan.

But in pouring them into Afghanistan as quickly as it takes them out of Iraq, Britain risks sinking into a conflict that may be much harder to leave.

Today a joint report from the United Nations Office on Drugs and Crime and the World Bank is expected to argue that counter-narcotics efforts have made the situation worse, by hurting the poorest and concentrating the trade in the hands of the barons.

Britain, which is spending £70 million in three years on the drugs effort alone, took a lead role in the anti-narcotics drive in Afghanistan largely because of the link it perceived with the heroin trade in Britain.

But it has been too ambivalent: first trying to wipe out poppy farming, then reining back, fearing social disruption, and trying to promote change through other local development.

The muddle has appalled the US, which never wanted a “war on drugs”, after its efforts in Central America, and would prefer Britain to focus on the “war on terror”.

Meanwhile, Lieutenant-General David Richards, the British commander in charge of Nato forces in Afghanistan, has waged a noisy campaign to advertise his lack of resources.

This week’s Nato summit emphasises how few countries — Britain, the US, Canada, the Netherlands and non-Nato Australia — have been willing to accept the burden of the fighting.

In taking Britain out of Iraq and further into Afghanistan, Blair may have hoped to find himself in a less controversial fight. But legitimacy does not make it easily winnable. Britain’s adroitness at getting out of Iraq has not yet been matched by its skill at getting into Afghanistan.

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