War, said Clausewitz, is the continuation of politics by other means. The Times reported this week on a distinctive political strategy adopted by Italy in the war in Afghanistan. Italian intelligence officers have paid money, amounting to tens of thousands of dollars, to the Taleban in protection money. Under the arrangement, neither side would attack the other.

When the Italians were replaced by French troops in the Sarobi district of Afghanistan last year, the newcomers believed the region to carry only a low risk, as there had been only one Italian fatality in the previous year. But the Italians neglected to mention the payments. Within a month of their arrival, ten French soldiers were killed and 21 were wounded in a Taleban attack.

The Italian Government has furiously denied our report, including our statement that the US Ambassador submitted a formal complaint about Italian payments to local insurgents in Herat province. Opposition politicians in France are demanding explanations, and ought to receive them. We unreservedly stand by our account. Since its publication, a Taleban commander and two senior Afghan officials have confirmed that this strategy has been practised by Italian forces in this and other regions of Afghanistan.

The Italian strategy is a scandal. It is important to be clear how and why. Clausewitz’s famous dictum is often misinterpreted. The politics that the great military thinker referred to included not only the chosen goals of the State but also the external conditions within which they were pursued. And adjusting the goals to fit the constraints is part of any military strategy that has a prospect of success.

The fortunes of the US-led coalition in Iraq were transformed by the appointment in late 2006 of a new military command that had thought deeply about the requirements of successful counterinsurgency. The new strategy recognised that political gains could not be made till security was established in Baghdad and the surrounding areas. With a surge in Allied troop levels, coalition commanders deliberately sought those local elements of the insurgency that were biddable, and bid for them. The strategy was to fracture a highly heterogeneous set of forces, leaving the remnants of irreconcilable Islamist and Baathist fanaticism.

It was a calculated risk. It worked. Al-Qaeda sustained serious damage and lost important sanctuaries in Baghdad and Anbar provinces. Instead of flooding into the country, foreign jihadists turned and fled. That is the outcome that Afghanistan needs, for the welfare of its people and for Western security. It is reasonable, and conceivably even far-sighted, for coalition forces to use economic inducements to scatter the Islamist enemy. That approach would be wholly consistent in principle with the observation of General Stanley McChrystal, the Nato commander, that the coalition must operate in ways that minimise casualties and damage.

But it is unconscionable and dangerous for a nation within the coalition to pursue a unilateral strategy without consulting their allies. The campaign against the insurgents is a collective operation, conducted through Nato, designed to provide collective security. There is a role for local deals. However unprincipled they may appear to the purist, they are far preferable to the tortuous drip of military strikes that inadvertently kill and maim civilians, and cost the counterinsurgency public support.

Deals that are negotiated locally cannot be deals that are negotiated separately, however. That is the route to Allied discord, disarray and unnecessary death. That is the charge against Italy’s strategy in Afghanistan. Silvio Berlusconi’s Government must answer it.