General David Petraeus said that the challenges in Afghanistan were “serious”, that they required a sustained and substantial commitment and that there were “no quick fixes”.

The new head of the British Army, General Sir David Richards, also warned last night that Nato had yet to find the right formula for success in Afghanistan. General Richards also warned that defeat for the international coalition would have an “intoxicating impact” on extremists around the world. Failure for an alliance as powerful as the Nato presence in Afghanistan would convice terrorists that “anything might be possible”.

The two generals were speaking after a soul-searching summer marked by a rising number of casualties. Since 2001 BritainÂ’s death toll has reached 216 and AmericaÂ’s 830. But both men insist that the mission is achievable.