President Obama's decision to deploy up to 250 additional U.S. troops beyond the 50 already in Syria is a welcome development in the fight against the Islamic State of Iraq and the Levant (ISIL). But it's important to recognize that achieving the stated U.S. goal of degrading and ultimately defeating ISIL will not occur soon with such incremental increases.

Putting together a coalition that could make a decisive difference — an effective indigenous force augmented by troops from a regional Arab, Sunni nation — remains an elusive goal, meaning the fight against ISIL likely will continue to be a slog.

The fight is especially essential to free those suffering under ISIL rule. But also because ISIL "is trying hard to replicate the massacres" in Paris and Brussels, as well as elsewhere in Europe and North America, Frederic Hof, a former special adviser for the transition in Syria who is now a senior fellow at the Atlantic Council, told an editorial writer.

ISIL is more "virulent" than Al-Qaida because it's also a quasi-state with an army that not only has attacked Europe but that also has destabilized Iraq and other Mideast nations, said James Jeffrey, a former ambassador to Iraq and Turkey who is now a senior fellow for the Washington Institute for Near East Policy. And yet, Jeffrey added, while "we're not good at fixing societies, 10-year campaigns in Iraq and Afghanistan, we are good at taking down [opposing] forces."

The additional troops will in fact be advising local forces fighting ISIL, and some progress has occurred. But a much more robust presence is needed. Kurds have been effective fighters, but Sunnis need to hold their homelands. "The post-combat stabilization mission would be of transcendent importance, as we have learned in Iraq and Libya," Hof said.

Obama's reticence is understandable. He won the presidency, in part, by pledging to end the chronic conflicts in Iraq and Afghanistan and not to enter yet another major Mideast war. Americans seem to concur with this caution, and there's no clear sense that a dramatically ramped-up deployment would be advisable, let alone sustainable.

Yet absent U.S. leadership, it's unlikely that regional allies or other NATO nations will step up. And that's "a very risky approach, given the record of this bloody minded organization," Hof said.

Terrorism isn't the only risk. A metastasizing ISIL likely would swell the refugee wave, too. Obama announced the troop increase during a visit to Germany, a nation that has admirably led in resettling refugees. But the public pushback is growing in Germany and other European Union nations, and the rise of right-wing political movements rightfully concerns transatlantic leaders. Sadly, the throngs fleeing Syria will only grow until ISIL is not just degraded but defeated, and until a diplomatically difficult political settlement can end Syria's vicious civil war.

European and Mideast nations are most impacted by ISIL, but this is the world's fight. America can lead, but NATO and Arab allies must significantly step up their efforts, too.