Dec. 24 (UPI) -- Outgoing Defense Secretary James Mattis signed an order Monday to begin the withdrawal of U.S. troops from Syria.
A U.S. defense official said "the execute order for Syria has been signed," while a second confirmed Mattis was the one who signed it, CNN reported.
The execute order outlined how and when the withdrawal of U.S. forces from Syria, which is expected to take place in the coming weeks, will be carried out.
It puts into action an order by President Donald Trump Wednesday to conduct a "full" and "rapid" withdrawal of the 2,000 American troops fighting the Islamic State -- also identified by the acronyms ISIS and ISIL -- in Syria.
On Wednesday, Trump touted "we have defeated ISIS in Syria, my only reason for being there during the Trump Presidency" and that "after historic victories against ISIS, it's time to bring our great young people home!"
The decision was met by criticism from several members of Congress who sent a letter to Trump asking him to reverse his decision, saying "such action at this time is a premature and costly mistake that not only threatens the safety and security of the United States, but also emboldens ISIS, Bashar al-Assad, Iran and Russia."
Mattis, who was also opposed to withdrawing troops from Syria, cited differences with Trump in his resignation letter Thursday, saying the president "deserves a military chief "whose views are better aligned with yours."
On Sunday, Trump announced Mattis' deputy, Patrick Shanahan, would take on the role of defense secretary at the start of the new year -- two months before Mattis planned to retire.