If.

Two letters long, it is arguably the most fruitless word in the English language, an evocation of paths not taken, possibilities foreclosed, regrets stacked high — and it lies like a pall of smoke over President Obama’s Wednesday-night announcement that this country is returning to war, albeit with air strikes only, in a place we just left behind in 2011 after spending almost nine years, over a trillion dollars and 4,425 lives.

If.

As in, if President Bush had concentrated on toppling the Taliban in Afghanistan, which harbored the authors of the terrorist strike we suffered 13 years ago last week, if he had not rushed to judgment, convincing himself Iraqi dictator Saddam Hussein was behind the attack, if his administration had not used suspect intelligence to claim Hussein possessed weapons of mass destruction, if we had not bought into the fantasy that we could impose a Jeffersonian democracy on another nation and have them thank us for it, if we had not destabilized the region, if we had never kicked this hornet’s nest, would we now find ourselves obliged to confront the criminal gang that calls itself the Islamic State?

It’s doubtful, to say the least.

And one imagines that as he wrestled with Wednesday’s decision, this president who came to office vowing to end the Iraq War felt not unlike Michael Corleone in Godfather Part III: “Just when I thought I was out, they pull me back in!”

Granted, Obama’s predicament is hardly unique. Lincoln had to fight the war Buchanan’s dithering made inevitable. Roosevelt had to fix the economy whose collapse Hoover had placidly watched. Washington was probably the last president who didn’t have to clean up his predecessor’s mess.

So once more unto the breach. What other choice do we have? With stunning speed that has alarmed the world, the Islamic State has seized large swaths of Iraq and its civil war-wracked neighbor, Syria, marching toward its stated goal of establishing a caliphate. In the process, it has committed acts of genocide and atrocity, including the beheading of two brave American journalists. We can hardly stand by and do nothing. In opting for air strikes, the president has probably chosen the least bad from a palette of unattractive options.

Yet as we go again to war, there is one last “if” we ought to heed, for it concerns not the failings of a president but those of the people. So many of us bought into the Bush administration’s false conflation of Iraq and the Sept. 11 attacks, even when it became clear there was no connection. And so many of us echoed the administration’s shrug of indifference when the weapons of mass destruction turned out to be mirages of mass delusion.

Shorn of his two major rationales for going to war, you may recall, Bush said that, even knowing what he now knew, he still would have invaded Iraq. And the American people echoed this bizarre nonchalance, 56 percent telling Gallup in 2003 that they supported the war whether weapons were found or not. Thus, we enabled a long and unnecessary war.

Had we the people not been so morally craven, we might have saved much treasure and blood. Had we had not been so panicked and credulous, America might not have created the vacuum into which this new threat now rushes.

The lesson has resonance not simply for the past, which is unalterable, but also for the future, which is unwritten. As a free people, it is our job to apply a brake, when necessary, to the excesses — particularly the military excesses — of our government. We owe that to the men and women who fly into harm’s way on our behalf, because we ought to be able to justify their sacrifice with more than fantasy, delusion, mirage and regret.

And, because if is about the most useless word there is.

Leonard Pitts Jr. is a columnist for the Miami Herald. Readers may write to him via email at: lpitts@miamiherald.com.