President Barack Obama has ordered a major but temporary escalation of the war in Afghanistan, sending an additional 30,000 US troops within six months while pledging to a sceptical American public that he would begin bringing forces home in July 2011.
Unveiling a long-awaited speech that followed three months of deliberation, the president said his new policy was designed to "bring this war to a successful conclusion".
The troop buildup will begin almost immediately, with 9,000 US marines expected to be in place by Christmas in Helmand for an offensive alongside British forces against Taliban strongholds, according to officials on both sides of the Atlantic.
The president said he was confident that more Nato allies would follow Britain’s lead and supply extra troops, though only a handful have so far suggested they will.
“Our friends have fought and bled and died alongside us in Afghanistan,” he said in the address to cadets at the West Point military academy. “Now, we must come together to end this war successfully. For what’s at stake is not simply a test of NATO’s credibility – what’s at stake is the security of our allies, and the common security of the world.”
Mr Obama rejected criticism that he had taken too long to form his new strategy, after commissioning 36 reports and holding nine meetings with his national security team. There were no troops ready to deploy before now, he said.
He reaffirmed an “over-arching goal” set out in March to “dismantle, disrupt and defeat” al-Qaeda on both sides of the Afghanistan-Pakistan border.
"We must deny al-Qaeda a safe haven," he said. "We must reverse the Taliban's momentum...and we must strengthen the capacity of Afghanistan's security forces and government."
His goal regarding the Taliban was however limited to preventing the Islamist militia from overthrowing the government in Kabul.
With American public opinion divided about whether or not more troops should be sent to a conflict that has lasted eight years and is in its deadliest phase, Mr Obama stressed to Americans that he believed the war was in their interests.
Summoning up images of the 9/11 attacks plotted by Osama bin Laden and al-Qaeda from their sanctuary in Afghanistan, he said that terrorists sent from the region had recently been arrested in the US.
“This danger will only grow if the region slides backwards, and al-Qaeda can operate with impunity. We must keep the pressure on al-Qaeda, and to do that, we must increase the stability and capacity of our partners in the region,” he said.
Stressing that Washington would deepen and broaden its political, economic and strategic partnership with Pakistan, he painted a dire vision of a failure there.
“The stakes are even higher within a nuclear-armed Pakistan, because we know that al-Qaeda and other extremists seek nuclear weapons, and we have every reason to believe that they would use them. These facts compel us to act along with our friends and allies.”
But it was the promise to begin withdrawing troops in July 2011, just a year after the US contingent will have reached full capacity, that brought most criticism of the president.