President Trump announced Sunday that Defense Secretary James Mattis will be leaving the administration on January 1, weeks earlier than planned and just days after Mattis' bombshell resignation letter made clear his policy disagreements with the White House.
"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 Sunday morning. "Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing. He will be great!"
In his resignation letter Thursday, Mattis, 68, had said he would remain in his role for more than three months. On Thursday, Trump similarly announced that Mattis was retiring in February.
"The end date for my tenure is February 28, 2019, a date that should allow sufficient time for a successor to be nominated and confirmed as well as to make sure the Department's interests are properly articulated and protected at upcoming events to include Congressional posture hearings and the NATO Defense Ministerial meeting in February," Mattis wrote.
Sources told Fox News this week that Mattis' resignation was "in protest" over the president's national security policies and that more resignations could be coming. U.S. officials said this week that the Trump administration is making plans to pull all 2,000 troops out of Syria, and Trump later tweeted that "we have defeated ISIS in Syria, my only reason for being there during the Trump Presidency."
Ground troops moved into Syria in 2015 to combat ISIS in the region, amid an escalating Syrian civil war. Trump had talked about pulling out of Syria before, but military leaders had warned about ISIS re-emerging should the U.S. do so. There is also concern about abandoning the U.S.' Kurdish allies.
The news that Mattis will be leaving sooner than expected comes just days after Brett McGurk, the U.S. envoy for the global coalition to defeat Islamic State (ISIS), on Saturday accelerated his planned departure and announced his resignation.
-- Fox News' Adam Shaw and The Associated Press contributed to this report.