It is incorrect to say that the world learned nothing new from Britain's Iraq Inquiry Committee, whose final report landed last week, just in time to further sour the British on their politicians. Any document that makes Tolstoy look like a short story writer is bound to yield some novel insights into the fateful 2003 decision that may forever haunt the conduct of Western foreign policy.

Yet, in its 2.6 million words, the report only managed to reinforce the accepted wisdom about former U.S. president George W. Bush's invasion of Iraq, and ex-British prime minister Tony Blair's complicity therein, rather than shed light on how to make decisions in the fog of war.

We already knew that the invasion of Iraq was based on mistaken intelligence about Saddam Hussein's possession of weapons of mass destruction, that the U.S.-led military coalition gave little thought about what a post-Saddam Iraq would look like before invading and that the generals were initially clueless about how to wage war against a Sunni insurgency.

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The sight of a sobbing Mr. Blair having to once again submit to a public flogging means that the main consequence of the report by Sir John Chilcot's committee will be to harden the kind of "intervention chill" that has led Western powers to tiptoe around, rather than confront, festering global menaces. The latter has already resulted in an unprecedented humanitarian disaster in Syria, the Islamic State and an emboldened Russian President Vladimir Putin.

"Now our failure to act in Syria has led to 400,000 dead and perhaps the largest humanitarian crisis in the world, with nearly five million refugees," Mr. Blair's former chief of staff, Jonathan Powell, wrote in The Times of London on the eve of the Chilcot report's release. "We may have thought we were smart, learning the lessons of Iraq by avoiding involvement. Instead we have realized painfully that not intervening in humanitarian crises and dictatorships may have an even more severe impact on our lives than doing so."

Mr. Bush, in 2008, negotiated the Status of Forces Agreement (SOFA) that foresaw a full withdrawal of U.S. troops from Iraq by 2011. By then, the country had largely stabilized, following the 2007 U.S. troop surge and so-called Sunni Awakening. But removing all U.S troops from Iraq turned out to be as a bad a move as the war itself. It led to renewed sectarianism – with a Shia-led government drawing closer to Iran – and the emergence of the Islamic State.

The latter seized on the chaos in Syria, which had by 2011 descended into civil war, to spread its tentacles. U.S. President Barack Obama's reluctance to enforce his own red line – which Syrian President Bashar al-Assad crossed by using chemical weapons on civilians – sent a message to bullies everywhere that, post-Iraq, their aggression would be tolerated by Washington and its allies. That's how we got Mr. Putin's annexation of Crimea and him calling the shots in Syria to prop up Mr. Assad.

Mr. Obama eventually came around to launching air strikes against the Islamic State in Iraq and Syria. But by then it was too little, too late. The main cause of the Syrian refugee crisis remains Mr. Bashad's own brutality, which he continues to exercise on his own people with impunity. Half the country's prewar population of 23 million has been displaced, creating a flood of refugees so large it threatens the stability of neighbouring countries and survival of the European Union itself.

"The moral rationale for taking steps to end the deaths and suffering in Syria, after five years of brutal war, is evident and unquestionable," more than 50 U.S. State Department officials said in an internal memo, expressing their dissent with the administration's Syria policy, that was leaked last month to The New York Times. "The status quo in Syria will continue to present increasingly dire, if not disastrous, humanitarian, diplomatic and terrorism-related challenges."

For all of the Chilcot report's criticism of Mr. Bush and Mr. Blair for "undermining" the authority of the United Nations Security Council by going to war without its authorization, one need only look at the UN's utter impotence in enforcing even its weakest Syria resolutions. Butchers have never been cowed into behaving by the UN, especially not when they have Russia on their side.

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Military Intervention is sometimes the worst foreign policy option, except for all of the others. The West must never let the mistakes of the Iraq war obscure that truth.