Despite the deaths of as many as half a million people, dozens by chemical weapons, in the Syrian civil war, the Trump Administration is now prepared to accept President Bashar al-Assad’s continued rule until Syria’s next scheduled Presidential election, in 2021, according to U.S. and European officials. The decision reverses repeated U.S. statements that Assad must step down as part of a peace process.

As recently as October, after a swing through the Middle East, Secretary of State Rex Tillerson said, “The United States wants a whole and unified Syria with no role for Bashar al-Assad in the government.” He told reporters travelling with him, “The reign of the Assad family is coming to an end. The only issue is how that should that be brought about.”

The U.S. decision reflects the Administration’s limited options, the military reality on the ground, and the success of Syria’s Russian, Iranian, and Hezbollah allies in propping up the beleaguered Assad regime. In a surprise visit to Syria, on Monday, Russia’s President Vladimir Putin declared victory against both ISIS jihadis and Western-backed rebels. “In just over two years, Russia’s armed forces and the Syrian Army have defeated the most battle-hardened group of international terrorists,” Putin told Russian forces stationed at an airbase in Syria’s coastal province of Latakia. Russia’s decision, in 2015, to provide air power to Assad is widely considered the pivotal turning point for the regime, which has now defied steep odds to hold on to power.

Washington also intervened in Syria, although primarily to fight ISIS. Since 2014, the United States has spent more than fourteen billion dollars—an average of more than thirteen million a day—in its air campaign against the Islamic State’s pseudo-caliphate. It also deployed two thousand U.S. troops to advise the Syrian Democratic Forces, a rebel militia that ousted ISIS from its capital, in northern Raqqa, in October.

Yet, over the past few months, facts on the ground have led the Administration to accept that Assad, whose family has ruled Syria for almost a half century, may be around for as much as four more years. Syria now controls the majority of territory—including cities such as Damascus, Hama, Homs, Latakia, and Aleppo, which was once the opposition’s crown jewel—that U.S. analysts refer to as “useful Syria.” The regime and its foreign allies—Russia, Iran, and Lebanon’s Hezbollah—have consolidated what were, a year ago, unconnected patches of territory. And Assad’s rule has been restored over the majority of the Syrian population.

Since October, the ouster of ISIS, which once held about a third of Syria, has shifted the international focus to the original civil war—and how to end it. Again, Assad is winning, partly courtesy of his allies and partly by default. The Syrian opposition groups backed by the United States have been ineffectual. They have squabbled among themselves and split into factions. No powerful leadership has emerged in almost seven years—since the Arab Spring uprising, in 2011, devolved into a civil war—to offer a viable alternative to Assad. Their demand that Assad step down as a precondition to peace or a political transition has become increasingly unrealistic.

Diplomatically, Washington has been marginalized by the powerful troika of Russia, Iran, and Turkey, which now dominates the peace process. Several rounds of talks sponsored by the United Nations, in Geneva, have made no progress. The U.N. effort has been superseded by the Russian-led troika’s peace talks, launched in January, held in Astana, Kazakhstan. After his visit to Syria, Putin flew to Turkey to discuss the next steps in that process with President Recep Tayyip Erdoğan.

In its early days, the Trump Administration had hoped that Syria would be an issue on which it could achieve coöperation and compromise with Russia. But in April, in one of his first military decisions, the President ordered a U.S. missile strike on a Syrian base that was used to launch chemical weapons on Khan Sheikhoun, a town under rebel control. More than eighty people were killed. “Using a deadly nerve agent, Assad choked out the lives of helpless men, women, and children. It was a slow and brutal death for so many,” Trump said. “Even beautiful babies were cruelly murdered in this very barbaric attack. No child of God should ever suffer such horror.”

Trump took a personal shot at Assad. “Years of previous attempts at changing Assad's behavior have all failed, and failed very dramatically,” he said. “Tonight, I call on all civilized nations to join us in seeking to end the slaughter and bloodshed in Syria, and also to end terrorism of all kinds and all types.”

But, given the political and military realities, U.S. officials have now concluded that any transition of power would depend on a credible election conducted by the United Nations. And the physical realities in Syria today are just as tough. Vast swaths of cities—homes, businesses, schools, health-care facilities, and infrastructure such as electricity grids and roads—have been destroyed. More than five million of Syria’s roughly twenty-two million people have fled the country, with twice as many more forced from their homes inside Syria. The prospect of holding a free and fair election in Syria—one that also includes the millions of refugees scattered in dozens of countries—will be an unprecedented challenge, diplomats told me. It will also take time for a new and more credible Syrian opposition to emerge.

The Trump Administration says it still wants a political process that holds the prospect of Assad’s departure. But it has concluded that it may take until 2021, when the next election is scheduled, to pull it off. Depending on the outcome of the 2020 U.S. election, Assad could still be in power after Trump leaves office. U.S. officials worry that Assad could win the 2021 Syrian election, one way or the other, and remain in power for years to come.