Thousands of US Marines stormed into the Helmand river valley under cover of night yesterday, the opening phase of Barack Obama’s new high-risk strategy in Afghanistan.

In Operation Khanjar, or Strike of the Sword, hailed by one commander as a “D-Day moment”, 4,000 Marines entered the lower Helmand river valley, hoping to do in hours what British troops have failed to do in three years.

It is part of a massive surge ordered by Mr Obama, doubling the number of American troops and flooding Helmand with 10,000 Marines — far in excess of the 8,000-strong British contingent stationed there since 2006.

Operation Khanjar aims to capture and hold a swath of Taleban territory, opening the way for a massive influx of development aid and allowing the Afghan Government to put down roots before its presidential election on August 20. The election is a critical test for the leadership of President Karzai, once a darling of the West, now tainted by accusations of corruption and ineffectuality yet still regarded as Afghanistan’s least bad option.

Helmand, a Pashtun heartland, ought to be Karzai country, but with a scant government presence it has largely been lost to the Taleban, who rule with an iron grip. British forces have struggled to project across the province, maintaining only small islands of calm and being forced repeatedly to relinquish ground captured in fighting because of a lack of troops. US commanders said that the lesson had been learnt and insisted that this operation was different.

“What makes Operation Khanjar different is the massive size of the force, the speed at which it will insert, and that where we go we will stay, and where we stay, we will hold,” Brigadier-General Larry Nicholson, the Marines’ commander said.

The area south of the British headquarters at Lashkar Gah is the world’s biggest heroin-producing region and a crucial transit point for Taleban fighters joining the insurgency from over the border in Pakistan. Much of the ground the US Marines aim to seize has never been trodden by foreign troops. British forces failed to penetrate south of Garmsir, where new fighters arriving from Pakistan are blooded in battle. American frustration with the British strategy saw them move into the area in 2008.

Taleban commanders vowed yesterday to repel the attack with fighters from all over the south. “Thousands of Taleban Mujahidin are ready to fight,” Mullah Hayat Khan, a senior commander, told Reuters. Early reports from the battlefield, however, suggested that the Taleban were putting up minimal resistance. “The enemy has chosen to withdraw rather than engage for the most part,” Lieutenant Abe Sipe, a Marine spokesman said.The Taleban have had years to dig in around the valley’s dense foliage and irrigation ditches and a long and bloody engagement like the one the British had risks eroding domestic support for the war. The Marines’ first objective is to clear the valley of insurgents long enough for elections to be held and for civilians to feel the Government’s effect, in some cases, for the first time. As the first district, Khanishin, was captured yesterday, Afghan troops hoisted the national flag.

One sign of a new approach is Washington’s announcement, days ago, that it was ending its policy of aggressive poppy eradication, safeguarding the livelihood of Helmand’s thousands of opium poppy farmers. Mr Obama said yesterday that the main goal in Afghanistan was to prevent al-Qaeda from training fighters and launching attacks on the US.

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