U.S. President Donald Trump has begun what will be a total withdrawal of U.S. troops from Syria, declaring on Wednesday they have succeeded in their mission to defeat Islamic State and were no longer needed in the country.
A decision to pull out completely, confirmed by U.S. officials and expected in the coming months, coincides with the roughly 2,000 U.S. troops finishing up a campaign to retake territory once held by Islamic State militants.
But it could leave the United States with few options to prevent a resurgence of Islamic State. It could also undercut U.S. leverage in the region and undermine diplomatic efforts to end the Syrian civil war, which is now in its eighth year.
"They're all coming back and they're coming back now. We won," Trump declared on Wednesday in a video posted on Twitter, titled "After historic victories against ISIS, it's time to bring our great young people home!"
News of a full withdrawal drew immediate criticism from some of Trump's fellow Republicans, who said that the U.S. withdrawal would strengthen the hand of Russia and Iran, both of which support Syrian President Bashar Assad.
It may also leave an alliance of Kurdish and Arab militias known as the Syrian Democratic Forces, or SDF, exposed. The SDF has been among the most effective forces in combating Islamic State, but it is currently under threat as Turkey weighs a new offensive in Syria.
U.S. commanders on the ground, who have developed strong ties to SDF leaders, voiced concerns about what a hasty withdrawal would mean for the U.S-backed forces and were surprised by the decision, U.S. officials told Reuters, speaking on condition of anonymity.
But Trump said that he considered the mission in Syria over given Islamic State's territorial losses.
Trump's predecessor, Barack Obama, was slow to get involved in Syria's civil war, seeking to avoid being dragged into another open-ended foreign conflict like the one in Afghanistan. Hundreds of thousands of people have been killed in the conflict, which has displaced around half of Syria's pre-war population of 22 million.
But in a campaign to defeat Islamic State in Syria, Obama ordered airstrikes from September 2014 and then troops into the country the following year.
The White House declined to offer a timeline for the withdrawal.
One U.S. official said Washington aimed to withdraw troops within 60 to 100 days and said the U.S. State Department was evacuating all its personnel in Syria within 24 hours. A second official said they could leave even sooner.
Trump is wary of open-ended foreign conflicts and his decision on Syria raises questions about whether he may also reconsider the U.S. war effort in Afghanistan, where American forces have been fighting since 2001.
Trump reluctantly agreed to a troop increase last year but U.S. officials have privately acknowledged a sense of urgency and are increasingly focused on securing a peace deal with a resurgent Taliban.
Some of Trump's Republican allies in Congress railed against the pullout decision. U.S. Senator Lindsey Graham, often a Trump ally but generally a foreign policy hawk, said a withdrawal would have "devastating consequences" for the United States in the region and throughout the world.
"An American withdrawal at this time would be a big win for ISIS, Iran, Bashar Assad of Syria, and Russia," Graham said in a statement.
The surprise decision also raised eyebrows abroad.
Prime Minister Benjamin Netanyahu said Israel would study the decision and would ensure its own security.
A British defense minister said he strongly disagreed with Trump that Islamic State had been defeated in Syria.
In Russia, TASS news agency quoted the Foreign Ministry as saying withdrawing U.S. troops from Syria created prospects for a political settlement.
Many of the remaining U.S. troops in Syria are special operations forces working closely with the SDF.
The partnership with the SDF has helped defeat of Islamic State in Syria but has outraged NATO ally Turkey, which views Kurdish YPG forces in the alliance as an extension of a separatist militant group fighting inside Turkey.
Ankara is threatening a new offensive in Syria. To date, U.S. forces in Syria have been seen as a stabilizing factor and have somewhat restrained Turkey's actions against the SDF.
A complete withdrawal of U.S. troops from Syria would leave a sizable U.S. military presence in the region, including about 5,200 troops across the border in Iraq. Much of the U.S. campaign in Syria has been waged by warplanes flying out of Qatar and other locations across the Middle East.
Still, U.S. Defense Secretary Jim Mattis and State Department officials have long fretted about leaving Syria before a peace agreement can be reached.
Islamic State is also widely expected to revert to guerrilla tactics once it no longer holds territory. The U.S. has not ruled out that Islamic State's leader Abu Bakr al-Baghdadi could still be alive.
A U.S. withdrawal could open Trump up to criticism if Islamic State reemerges.
In the past, Trump lambasted Obama for withdrawing U.S. forces from Iraq, preceding an unraveling of the Iraqi armed forces. Iraqi forces collapsed in the face of Islamic State's advance into Iraq in 2014.
However, a senior administration official rejected the comparison to Iraq, where the U.S. had many more troops and would have stayed if Baghdad had provided legal protections for American forces.
"That's an apples and oranges comparison given the scope and scale of our engagement in Iraq," the official said.
Islamic State declared its so-called "caliphate" in 2014 after seizing large swathes of Syria and Iraq. The hard-line group established its de facto capital in the Syrian city of Raqqa, using it as a base to plot attacks in Europe.
According to U.S. estimates, the group oversaw about 100,000 square kilometers (39,000 square miles) of territory, with about 8 million people under Islamic State rule. It had estimated revenues of nearly one billion dollars a year.
A senior U.S. official last week said the group was down to its last 1 percent of the territory it once held. It has no remaining territory in Iraq.
Hajin, the group's last major stronghold in Syria, is close to being seized by U.S.-backed SDF forces.
After losing Hajin, Islamic State will control a diminishing strip of territory along the eastern bank of the Euphrates River in the area where U.S.-backed operations are focused. Militants also control some desert terrain west of the river in territory otherwise controlled by the Damascus government and its allies.
U.S. officials have warned that taking back the group's territory would not be the same as defeating it.
"The coalition has liberated the ISIS-held territory, but the campaign against ISIS is not over," Pentagon spokeswoman Dana White said in a statement."
