Nato launched the biggest combat mission of its 57-year history today when it took over an operation to quell a resurgence of Taleban, drug lords and al-Qaeda operatives in southern Afghanistan.

David Richards, the British Lieutenant-General leading the mission, also became the first Briton to command American troops in active combat since Field Marshal Montgomery in the Second World War.

Nato has conducted aerial bombing and peacekeeping operations in Bosnia and Kosovo — when US troops were also under British command — but that did not involve ground combat.

"It is hugely symbolically and practically important for Nato," said Lieutenant-General Richards, the head of the Nato-led International Security Assistance Force (ISAF) in Afghanistan.

"Are we up to it? I’m quite clear we are," he said. "I think in three to six months we can make a difference."

But he added later that Afghanistan would need the current level of military assistance for three to five years and some sort of foreign troop presence for up to 15 years.

Lieutenant-General Richards assumed command of the operation from the American Lieutenant-General Karl Eikenberry in a ceremony at an airbase in Kandahar, the former Taleban stronghold in southern Afghanistan.

Until today, ISAF’s 10,500 troops had operated only in the capital, Kabul, and the more stable north and west, where the central Government has established a degree of control.

Meanwhile, US-led coalition forces have been facing an increasingly fierce insurgency in the east and the lawless south, where much of the poppy crop in Afghanistan is grown.

That insurgency has escalated dramatically this year, claiming at least 1,700 lives since January, in the bloodiest violence in Afghanistan since the Taleban was toppled in late 2001.

Today eight people were killed by a bomb blast at a mosque apparently intended for a provincial governor in the eastern region of Nangarhar. More than 30 insurgents were killed in fighting in the south on Sunday.

ISAF, which now incorporates 37 different countries, will expand to 18,000 troops by October, with more than 10,000 deployed in the south in an attempt to bring the region under Kabul’s control.

Its strategy is to establish zones of stability, where "quick impact" development projects can be implemented to win over the local population and persuade them to stop cultivating poppies.

ISAF aims to secure one such "development zone" in each of the six southern provinces by the end of August, Lieutenant-General Richards said.

However, even he admitted that it was hard to know exactly what ISAF was up against.

"It’s a very complex picture," he said. "A lot of people who call themselves Taleban are not Taleban at all."

They were rather a combination of Taleban hardliners and foot soldiers, drug lords and their henchmen and tribal leaders pursuing their own agendas, he said.

He estimated that they numbered no more than a few thousand in the south and that the number of al-Qaeda operatives and other foreign fighters was minimal.

"Those few thousand who oppose the vast majority of the Afghan people and democratically elected Government should note this historic day and understand that they will not be allowed to succeed," he said at the ceremony today.

But other military and diplomatic sources attribute the sudden rise in the number of suicide bombings and improvised explosive devices this year to an influx of foreign militants, especially from Pakistan.

Many British troops are sceptical about the projected timeframe and intensity of the operation, given the fierce resistance encountered by the 4,000 British troops in the southern province of Helmand.

Among aid and development agencies, there are also grave concerns about launching reconstruction projects at the same time as undertaking such a huge combat operation.

"No doubt the security situation does restrict our ability to deliver development programmes," said Aleem Siddique, a spokesman for the United Nations Assistance Mission in Afghanistan.

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