President Donald Trump asked General Jim Mattis to leave his position as Secretary of Defense early, after his decision to resign.

“I am pleased to announce that our very talented Deputy Secretary of Defense, Patrick Shanahan, will assume the title of Acting Secretary of Defense starting January 1, 2019,” Trump wrote on Twitter.

Mattis resigned last week in protest at the president’s decision to withdraw troops from Syria. He planned to stay on until February to ensure a smooth transition.

The Washington, DC, political establishment expressed their alarm at Mattis’ decision, as many criticized Trump’s insistence on getting American troops out of the Middle East.

Trump asked Shanahan to take Mattis’ responsibilities right away.

“Patrick has a long list of accomplishments while serving as Deputy, and previously Boeing,” Trump wrote. “He will be great!”

On Saturday, Trump said that he gave Gen. Jim Mattis a “second chance” after he was forced out of Central Command by former President Barack Obama in 2013.

“When President Obama ingloriously fired Jim Mattis, I gave him a second chance. Some thought I shouldn’t, I thought I should,” Trump wrote on Twitter on Saturday.

I am pleased to announce that our very talented Deputy Secretary of Defense, Patrick Shanahan, will assume the title of Acting Secretary of Defense starting January 1, 2019. Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing. He will be great! — Donald J. Trump (@realDonaldTrump) December 23, 2018