Syrian refugees disembark from an overcrowded raft on the Greek island of Lesbos on Friday. (Yannis Behrakis/Reuters)

President Obama is right about the 10,000 Syrian refugees. But what about the other 3,990,000?

Obama has chastised Republicans for betraying American values since the terrorist attacks in Paris. He wants the nation to accept 10,000 people fleeing Syria’s horrific civil war, and Republicans want to turn them away. GOP presidential candidates have contemplated registering Muslims, compared Muslims to dogs and advocated welcoming Christians only. It is, all in all, disgusting.

But sheltering even 10,000 refugees, of any faith, would have mostly symbolic value. Four million Syrians have fled, with even more internally displaced. Half of all Syrians have been forced from their homes.

For that, the Obama administration bears some responsibility — and the reasons should be something voters think about in 2016.

Obama came into office in 2009 determined to end the country’s long wars in the Middle East and Central Asia. He wanted to focus on what he considered more important regions (Asia and the Pacific) and goals (restoring the U.S. economy, controlling nuclear weapons).

He withdrew all U.S. troops from Iraq when experts advised that a residual force of 15,000 would help to keep a fragile peace. He bombed Libya to overthrow its dictator but opposed a small NATO training force that might have stabilized the new government. He ordered a limited surge of troops to Afghanistan but soon began withdrawing them on a timetable unmoored to conditions. When Syrian dictator Bashar al-Assad cracked down on democracy protesters, kindling violence, Obama kept the United States aloof.

It’s impossible to know what would have unfolded had he decided differently. We do know that the outcome in three of these cases has been catastrophic (with Afghanistan still hanging in the balance) — and quite different from what the president expected.

At the United Nations two years ago, Obama boasted that without his intervention, Libya “would now be engulfed in civil war and bloodshed.”

You can still find, on the White House Web site, “Remarks by the President on Ending the War in Iraq,” in which he expresses confidence that Iraqis would “build a future worthy of their history as a cradle of civilization.”

That same year — 2011 — he said, “It is time for the Syrian people to determine their own destiny, and we will continue to stand firmly on their side.” As conditions deteriorated the next year, he said, “we want to make sure that the hundreds of thousands of refugees that are fleeing the mayhem, that they don’t end up creating — or being in a terrible situation, or also destabilizing some of Syria’s neighbors.”

Today Libya is “engulfed in civil war and bloodshed.” In Iraq, having lost leverage and interest, the United States stood aside as the Shiite prime minister turned the U.S.-trained armed forces into a sectarian militia that gave space and impetus for radical Sunnis — reborn as the Islamic State — to reemerge. In Syria, effects even direr than Obama feared from U.S. intervention bloomed in its absence: a wider war, spilling across borders; radical jihadists establishing the kind of statelet that al-Qaeda never achieved; millions of refugees destabilizing not only Syria’s neighbors but all of Europe.

Some conclude from all this that the United States should not get involved because we lack the staying power to see a job through. Given our spasms of intervention and withdrawal, the argument sounds sensible.

President Obama urged the American public not to give in to fear surrounding refugees in the wake of the Paris attacks. (Reuters)

But it has two flaws.

First, it’s not true. U.S. troops remain in South Korea more than six decades after the Korean War, and few Americans object. U.S. troops remain in Kosovo more than 15 years after that war, and few Americans even know. If Obama had chosen to station a small contingent in what was in 2011 a largely peaceful Iraq, most Americans would have accepted the decision.

More important, nonintervention doesn’t work. As recently as last year, Obama was putting Syria in the basket of problems that don’t threaten our “core interests” and maintaining that “today’s principal threat . . . comes from decentralized al-Qaeda affiliates.” Today it seems obvious that the Islamic State cannot be ignored or even just contained.

The choice is not between invasion and inaction. What’s needed is relatively modest levels of persistent engagement — diplomatic, economic and military — that might keep the United States from facing the dire choices that now loom again.

The leadership challenge is that while a problem is manageable, it also seems, to Congress and the American people, less urgent. By the time a threat becomes existential, it is also much harder to defeat. Presidential candidates who tell us this year that jihadist terrorism is someone else’s problem are selling us a bill of goods. But so are candidates who say we can quickly dispose of the threat and then come home.

Last month, even as he announced a longer deployment in Afghanistan, Obama was still saying , “As you are well aware, I do not support the idea of endless war.”

Unfortunately, wars do not end unless both sides agree — or one side is defeated.

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