Syria’s continuing physical and political destruction is so severe that it is hard to believe the country can be put together again.

The human repercussions are enormous and can also be felt throughout the Middle East, particularly Turkey. Whatever his dictatorial ways, Turkish President Erdogan has been an impressive humanitarian, welcoming over two million Syrians and counting into his country. His helpful rhetoric on this unpopular issue in Turkey has been impressively strong.

Refugee flows are now growing in Western Europe, as hundreds of thousands of Syrians—as well as many from African nations plagued by conflict—seek refuge in a number of countries. Reception of fleeing Syrians in parts of Europe has been both welcoming and increasingly ugly. And this refugee flight is far from over, as many Syrians—from the government-controlled areas and the rebel territories alike—are still determined to get out of their homeland.

Even in the United States, whose present-year proposed numbers for accepting people fleeing the Syrian conflict are very small—some ten thousand—the refugee issue has reached national proportions, and increasingly touches upon the current presidential campaigns. Syrian refugees have also added a new dimension to the American discussion of Islam.

In the postwar world, the United States has been an extraordinary refugee-receiving country. Its most impressive manifestation has been President Jimmy Carter’s decision to parole into the United States over a million Indochinese refugees—a mixture of humanitarianism and guilt over our Indochina debacle. American leadership also propelled two international conferences to encourage other countries to take more Indochinese refugees, with not inconsiderable results. A number of states even adopted many Indochinese, such as the Hmong in Minnesota. But the Syrian refugee exodus to Western countries, including the United States, apparently contains factors that make reception more difficult at this time: Islamic fundamentalism, fears of terrorism among immigrants, along with general refugee fatigue.

The United States has once again taken the lead in generating international conferences to get countries to take more refugees and help pay for them. The administration has been willing to provide a substantial portion of the cost of maintaining Syrian refugees in Jordan, Lebanon, and Turkey. But most Middle East countries apparently have little interest in helping other Arabs, and do not want them in their countries. Nor do many Syrians want to go to Arab countries. The United States and Western European countries also have been less than receptive to the actual refugees themselves, having become increasingly concerned over the prospects of importing terrorism, and thus increasingly leery of taking in more Syrians, public protestations notwithstanding. This problem for Syrians (and other Arabs) is likely to grow, as is the animus to doing much about it in most countries.

In such moments, U.S. leadership has been an indispensable element in shaping global events. A political and military settlement to the Syrian conflict is beyond the capacity of this administration—it probably will take years of effort, and we already have fallen behind in that regard—but at the very least we can accept vastly more refugees than the modest numbers currently contemplated.

A significant, workable plan will require more than the government rhetoric we have now become accustomed to—it will need a willingness of the administration to put in some political capital toward raising the level of refugee admissions, and the financial aid needed to more seriously cope with this unending problem. This difficult problem means that this—and the next—American president has to take the lead to mobilize both greater domestic and international support, including not least from our Arab allies.

Mr. Obama has for the most part shown himself a humanitarian, both internationally and in the United States. But having allowed the Syria disaster to fester unabated by any serious American effort to stop it for nearly five years, he must step up his efforts in his final year in office, or he instead will be remembered as a spectator to the greatest humanitarian crisis in this new century.

Morton Abramowitz is a senior fellow at The Century Foundation and a former Ambassador to Thailand and Turkey.