The painful legacy of the Iraqi war has complicated US President Barack Obama's efforts to muster support for military action against Syria.
As a senator, Obama opposed the war in Iraq, and as president, he brought it to a close. But that war's end did not erase memories of the false premise on which president George W. Bush built a case for the US-led bombing campaign and ground invasion.
Ten years ago, Bush urged the American public, Congress and the international community to believe intelligence assessments that Saddam Hussein's government possessed weapons of mass destruction - a claim later proved wrong.
Now Obama is holding Syrian President Bashar al-Assad responsible for a reported chemical weapons attack and saying that justifies military action against the Damascus government. But there are doubts about whether the evidence is convincing.
"The well of public opinion was well and truly poisoned by the Iraq episode and we need to understand the public scepticism," British Prime Minister David Cameron said during Parliament's debate that led to a stunning and unexpected refusal to endorse military action against Syria.
Cameron and Obama argue that Iraq and Syria are vastly different in both the evidence in hand and the consequences.
Iraq did not possess weapons of mass destruction. In Syria, there is little doubt that civilians were killed by chemical weapons. The question is whether the US can pin the blame beyond doubt on Assad's government.
Supporters of Assad's rule, including Russia, have been quick to point to history in objecting to any retaliatory strikes against Syria. "All this is reminiscent of events from a decade ago, when the United States bypassed the UN and used fallacious information on the presence in Iraq of weapons of mass destruction to launch an adventure, the consequences of which are known to all," said Alexander Lukashevich, a Russian foreign ministry spokesman.
As US officials assembled and double checked data, Iraq was not far from their thoughts.
"Our intelligence community has carefully reviewed and re-reviewed information regarding this attack," Secretary of State John Kerry said on Friday. "And I will tell you it has done so more than mindful of the Iraq experience. We will not repeat that moment."
But even without the intelligence failures preceding the Iraqi war, there is an Iraq and Afghanistan war fatigue that has settled over the country that also poses challenges for Obama.
An NBC poll found that nearly eight in 10 Americans want Obama to obtain congressional approval before using force in Syria. That said, the public is more favourably disposed to a limited cruise missile launch than some other type of intervention, with 50 per cent favouring that kind of action and 44 opposing it.
Michael O'Hanlon, a national security analyst at The Brookings Institution, said that for all the contrasts with the 2003 Iraq invasion, the more apt comparison in Syria is with missile strikes ordered against Iraq by president Bill Clinton, including strikes in 1998 to punish Saddam for not complying with UN chemical weapons inspections.
"I'm surprised this administration doesn't make that analogy," O'Hanlon said. "This operation is going to be limited. It's going to be small scale or medium scale and it's going to be over as soon as it's begun practically."