There’s no way of knowing for certain to what degree U.S. foreign policy in the Middle East has led to the current refugee crisis in Europe.

Had the Obama administration’s support for the moderate Syrian opposition been robust and preemptive instead of delayed and weak, would Syria’s great cities remain populated, let alone still standing?

Had the president projected leadership and not retreated from his self-imposed “red line” on Bashar Assad’s use of chemical weapons, would Hungary’s razor-wire wall, meant to deter thousands of migrants from crossing its border, ever have been erected?

Had our political leaders been judicious enough to act when good interventionist options were still available instead of motivated by a politically expedient policy that embraced doing nothing, would more than 2,000 Syrians who drowned attempting to reach European shores this year still be alive?

We’ll never know.

But it’s impossible, in the wake of what some are calling the worst refugee crisis since World War II, to accept that the U.S. is somehow blameless in what has become a desperate and ugly reality.

Syria’s war has been raging for four years. More than a quarter-million Syrian civilians already have lost their lives in its crush.

Ancient cities of great historical and religious significance have been leveled.

Innocents have been intentionally targeted with barrel bombs and chemical weapons by an odious regime that has been surprisingly resilient, thanks to consistent support from Russia and Iran.

The prolonged chaos, coupled with President Barack Obama’s decision to leave no stabilizing ground force in neighboring Iraq, gave space and purpose for the Islamic State to not merely grow but flourish.

Its rise has further destabilized a region that has never suffered from a lack of volatility; and it is increasingly attracting fighters from the West.

In the wake of unthinkable violence, reportedly close to half of Syria’s population has fled their homes, more than 4 million taking refuge in neighboring states that are struggling to support them.

Many other Gulf States have closed their borders; others offer little in the way of opportunity, and so a stream of bedraggled migrants, close to 400,000 so far this year, has made the frequently perilous and sometimes fatal journey to European shores.

But the flow of people has not been easy to absorb.

Western nations, despite their wealth, are not necessarily equipped to deal with the immediate needs of so many refugees.

While some, like Germany, have made recent commitments to accept large migrant populations, others have been less receptive, and understandably so.

There are the long-term consequences of mass immigration, as described by New York Times columnist Ross Douthat, to consider “the realities of culture, the challenges of assimilation, the dangers and inevitability of backlash.” Nations have a responsibility to their own citizens first.

The rise of anti-immigrant attitudes on the European continent, and to a lesser degree in the U.S., has been dramatic in recent years; cultures have clashed, and the current crisis is likely to exacerbate the sentiments that feed those movements.

In Europe, as in the U.S., there is a palpable and legitimate fear the Islamic State will be able to infiltrate the West through the radicalization of some of the disaffected Syrian refugees that suddenly find themselves adrift in a strange new country, or that Islamic State operatives are already part of the refugee wave.

Claims by some observers that the migration itself — hijrah, or jihadist emigration — is a tactic of the terrorist organization don’t seem so far-fetched when considering the scope of the problem and its projected impact.

But the crisis and all of its many rippling effects were entirely foreseeable — expected even.

When the tiny body of Aylan Kurdi washed up on a Turkish shore last week, America appeared stunned.

Perhaps that is attributable to what Washington Post editorial director Fred Hiatt called “the most surprising of President Obama’s foreign-policy legacies … that he soothed the American people into feeling no responsibility for the tragedy.”

There is more the U.S. can and must do to aid those displaced by a conflict the West might have tempered with a long-term strategy for the Middle East.

And as we consider the consequences — many still to come — of the foreign-policy failures of the past two administrations, we may come to realize the costs of doing nothing are often just as grave as attempting to do too much.