Bagram - As he ponders leaving some troops in Afghanistan after the longest US war, Barack Obama harkens back to the 11 September 2001 attacks to justify more than a decade of sacrifice.
Whether the US president is also using that imagery to justify longer US military involvement in Afghanistan, senior political aides will not say.
But Obama, in a surprise visit to Bagram Airfield outside Kabul on Sunday, did not sound like a man about to wash his hands of Afghanistan.
Aides hint the president will offer some "clarity" on his intentions in a major speech at the West Point military academy on Wednesday meant to put his foreign policy in a wider context.
On Sunday, he twice mentioned that he saw a poster of the Twin Towers in New York in a Bagram trailer complex where he got a briefing from top military and intelligence officials.
Memory of 9/11 lives
Obama mentioned September 11 when talking to young troops, many of whom were mere kids when al-Qaeda sent fuel-laden airliners on suicide missions against targets in New York and Washington in attacks planned in Afghan terror havens.
He said he had just visited the new September 11 museum in the footprint of the World Trade Centre Twin Towers in New York - and there was a sense that he was squaring a circle in his mind on what to do next in Afghanistan.
"Once again, we resolved to never forget what happened on that September day and to do everything in our power to prevent something like that from ever happening again.
"That's why you are here. That's why you are here."
Despite warnings last year that the White House would contemplate leaving no troops in Afghanistan after combat soldiers ship home by the end of the year, Obama said several times during his four hours on the ground on Sunday that he was open to a future role for US troops in a training and anti-terror capacity.
He simultaneously played the role of the commander-in-chief bringing troops home and the statesman who would not leave Afghanistan to its fate.
Washington has been frustrated for months by Afghan President Hamid Karzai's refusal to sign a bilateral security agreement (BSA) that would offer legal protections to a residual force of US troops.
But US officials believe assurances by his two potential successors, Abdullah Abdullah and Ashraf Ghani, that they would sign up.
Obama's comments about September 11 were not the only striking aspects of his rhetoric during his Afghan trip.
He candidly said he was surprised at the performance of Afghanistan's fledgling armed forces, and stressed they were taking the lead in actions against the Taliban.
"I will be honest with you, it has gone better than I might have expected a year ago," he said.
While sceptics might question just how effective the Afghan force will be once Western troops have left, Obama's bluntness was striking.
Defence officials have told AFP they are "encouraged" that the president may be leaning toward a recommendation in the upper range of their hopes - around 10 000 troops for a residual US force.
There are political as well as strategic reasons why Obama may make that decision.
He was elected in 2008 on a platform of winding down foreign wars in Iraq and Afghanistan. But he always made a distinction between the two conflicts.
He branded Iraq as a "dumb" war, and recently in Manila said it was "disastrous".
He argued that Afghanistan had been neglected because of Iraq and promised to fix it - and as president sent tens of thousands of troops into battle.
There was always a suspicion that Obama's bullishness on Afghanistan offered him political cover in being anti-war on Iraq.
But the Afghan fight has perhaps proven more bloody and protracted than he had hoped.
More than 2 300 US troops have now died in Afghanistan and the Taliban is not yet defeated - although the administration can credibly claim to have devastated the core of al-Qaeda with ruthless drone strikes.
There is a clear sense that Afghanistan is "Obama's war".
While he pulled out all US troops from Iraq and was unable to agree a residual force in a country descending back into an inferno - that war will always be George W Bush's.
History would take a dimmer view of the current president's complicity if Afghanistan tips deeper into turmoil - and second term presidents are always thinking of their legacy.
Obama also risks being condemned by his own words if he leaves Afghanistan alone.
"We must realise that the 21st Century's front lines are not only found on the field of battle. They are found in the training exercise near Kabul, in the police station in Kandahar and in the rule of law in Herat," he said as a candidate in 2008.