“Having a big old fight is pointless and just making things worse,” said Captain Leo Docherty, of the Scots Guards, who became so disillusioned that he quit the army last month.

“All those people whose homes have been destroyed and sons killed are going to turn against the British,” he said. “It’s a pretty clear equation — if people are losing homes and poppy fields, they will go and fight. I certainly would.

“We’ve been grotesquely clumsy — we’ve said we’ll be different to the Americans who were bombing and strafing villages, then behaved exactly like them.”

Docherty’s criticisms, the first from an officer who has served in Helmand, came during the worst week so far for British troops in Afghanistan, with the loss of 18 men.

They reflected growing concern that forces have been left exposed in small northern outposts of Helmand such as Sangin, Musa Qala and Nawzad. Pinned down by daily Taliban attacks, many have run short of food and water and have been forced to rely on air support and artillery.

“We’ve deviated spectacularly from the original plan,” said Docherty, who was aide-de-camp to Colonel Charlie Knaggs, the commander in Helmand.

“The plan was to secure the provincial capital Lashkar Gah, initiate development projects and enable governance . . . During this time, the insecure northern part of Helmand would be contained: troops would not be ‘sucked in’ to a problem unsolvable by military means alone.”

According to Docherty, the planning “fell by the wayside” because of pressure from the governor of Helmand, who feared the Taliban were toppling his district chiefs in northern towns.

Docherty traces the start of the problems to the British capture of Sangin on May 25, in which he took part. He says troops were sent to seize this notorious centre of Taliban and narcotics activity without night-vision goggles and with so few vehicles they had to borrow a pick-up truck.

More damningly, once they had established a base in the town, the mission failed to capitalise on their presence. Sangin has no paved roads, running water or electricity, but because of a lack of support his men were unable to carry out any development, throwing away any opportunity to win over townspeople.

“The military is just one side of the triangle,” he said. “Where were the Department for International Development and the Foreign Office? “The window was briefly open for our message to be spread, for the civilian population to be informed of our intent and realise that we weren’t there simply to destroy the poppy fields and their livelihoods. I felt at this stage that the Taliban were sitting back and observing us, deciding in their own time how to most effectively hit us.”

Eventually the Taliban attacked on June 11, when Captain Jim Philippson became the first British soldier to be killed in Helmand. British troops have since been holed up in their compound with attacks coming at least once a day. Seven British soldiers have died in the Sangin area.

“Now the ground has been lost and all we’re doing in places like Sangin is surviving,” said Docherty. “It’s completely barking mad.

“We’re now scattered in a shallow meaningless way across northern towns where the only way for the troops to survive is to increase the level of violence so more people get killed. It’s pretty shocking and not something I want to be part of.”

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