Article snippet: MORE, who resigned in protest last week, would leave his job on Jan. 1, two months before his planned departure. Trump said in a tweet that Mattis’s deputy, Patrick Shanahan, will serve as acting Pentagon chief. “Patrick has a long list of accomplishments while serving as Deputy, & previously Boeing,” Trump wrote. “He will be great!” The abrupt decision comes as Trump's anger has boiled over at Mattis’s resignation letter, which was widely seen as a rebuke of the president's foreign policy. Senior administration officials said Trump chafed at negative media coverage of the letter, which featured a parade of lawmakers and retired military leaders appearing on cable news to criticize his leadership and praise Mattis’s resolve, and eventually reached a breaking point. Trump sent the tweet announcing Mattis’s early exit while at the White House, where he has spent the past few days after cancelling his Christmas trip to his Mar-a-Lago club in South Florida due to the government shutdown. Pentagon officials offered terse reactions to Trump’s announcement. “The secretary of Defense serves at the pleasure of the president. Sec. Mattis will work with Deputy Shanahan and department leadership to ensure that the [Defense Department] remains focused on the defense of the nation during this transition,” said Dana White, a spokeswoman for Mattis. Army Lt. Col. Joe Buccino, spokesman for Shanahan, said only that “the deputy secretary of Defense will continue to serve as ... Link to the full article to read more