“We will turn Afghanistan into a river of blood for the British,” he told The Times on a satellite telephone from an undisclosed location. “We have beaten them before and we will beat them again.”

That threat could once have been dismissed as the rantings of a dying movement that was driven from power by the US-led invasion of 2001. But today the warning will be taken seriously.

The Taleban have rearmed, recruited new followers and are planning a hot reception for the 8,000-strong Nato force from Britain, Canada and the Netherlands, which hopes to impose order on an area the size of Britain.

The deployment is intended to allow America to scale back its combat troops and help the Afghan Government to extend its writ beyond Kabul, the capital.

Lieutenant-General David Richards, the Briton in command of the Nato forces, said that he was not concerned about the threat and noted that his troops would “respond very robustly” if attacked.

But while Nato launched the “most challenging” ground mission of its history, the task looked increasingly daunting. “Outside of the main city and provincial towns everything is controlled by the Taleban,” Mullah Sayed Mohammed, an MP from Kandahar, said.

In Helmand province, assigned to the British, the Taleban sent a grim message yesterday to those who challenge their authority with the discovery of the beheaded body of a policeman.

Neighbouring Kandahar province is even more dangerous. Four Canadian soldiers were killed in a roadside bomb last month. In the worst recent clash, Canadian troops fought a pitched battle against a force of 200 Taleban in the Panjwai district, only a 20-minute drive from the city of Kandahar.

The Dutch, who are sending a force of only 1,000 men after a heated political debate at home, might have the most challenging task of all. They have been assigned southern Uruzgan province, a mountainous region, much of which is under Taleban control.

Veteran British forces in Afghanistan are convinced that they have a fight ahead of them. Eight Harrier fighter pilots based in Kandahar have never been busier, and the deployment of the fighter jets has been extended by six months.

Flight Lieutenant Scott Williams, 29, said: “I was here last year at the same time and the fighting is much fiercer this year.”

An incident on February 13 in the Deh Rawood district of Uruzgan illustrated the scale of the threat. When he flew over the scene, four American Special Forces were dead, killed by a massive roadside bomb. The US survivors were pinned between a ridge and a river and were taking heavy fire from Kalashnikovs and rocket launchers from a force several hundred strong.

“Every time I had radio contact with the guys on the ground I could hear gunfire in the background,” Flight Lieutenant Williams said. To try to suppress the threat he and his comrades flew over the area at an altitude of less than 100ft, hoping that the noise would scare off the Taleban.

It did not. A Harrier then fired a rocket into the group of insurgents. This, too, failed to subdue a stubborn and apparently well-trained enemy.

A Harrier then dropped a 540lb (245kg) airburst bomb, which can destroy an area the size of a football pitch.

“It’s not going to be pleasant after one of those has been dropped.” the pilot said. “Things went pretty quite.”

Explore World News

• Iraq News

• US & Americas News

• Europe News

• Middle East News

• Asia News

• Africa News

• Ireland News

Times Recommends

• Congo's rangers risk their lives to guard gorillas
• Pearl farming in China losing its lustre
• Axl Rose mystery as album arrives at last