UK troops in Afghanistan face fighting which is more intense and prolonged than any other conflict in the past 50 years, a British general has claimed.
British soldiers face "days and days of intense fighting", it is claimed
Some British soldiers will be withdrawn from lawless parts of Helmand province and replaced with Afghan troops, said Lt Gen David Richards.
He is commanding the Nato force in the country and has described the threat as "persistent low-level dirty fighting".
Extra helicopters and equipment were required to cope, he said.
"This sort of thing hasn't really happened so consistently, I don't think, since the Korean War or the Second World War," he told the BBC World Service.
"It happened for periods in the Falklands, obviously, and it happened for short periods in the Gulf on both occasions. But this is persistent low-level dirty fighting."
Gen Richards said he was proud of his troops and the battle was worth the problems.
"We can't afford for this country to go back to what it was," he said.
"We will soon feel the result of that when London gets attacked from a firm base where [enemy fighters] can do what they want."
But as a result, British soldiers were enduring "days and days of intense fighting, being woken up by yet another attack, and they haven't slept for 24 hours", he added.
His remarks came as the chairman of the Commons all-party defence committee revealed his concerns that the British operation in Afghanistan "was being done on a shoe string".
Conservative MP James Arbuthnot told BBC Radio 4's Today programme there was a feeling "that we are not spending enough money on the troops we are putting into danger, and that we are asking [them] to do extremely difficult things on our behalf".
The committee warned of a similar situation in Iraq. It called for patrol vehicles to be strengthened to provide greater protection, and for additional helicopters to be supplied.
Defence Secretary Des Browne has insisted that British forces were "stretched, but not overstretched".
William Hague, the shadow foreign secretary, said the Conservatives were "concerned that it could be necessary in the future to send more forces to Afghanistan".
"We think the government should be making the case now to our Nato allies to provide more troops from other Nato countries, so that it isn't just Britain that has to bear the brunt of that," he told BBC News.
"We'd like to see ministers more active in preparing that case for the rest of Nato, and we would like to see them look again at some of the equipment, not just to Afghanistan but to Iraq."