US President Donald Trump on Sunday said he was replacing Defense Secretary Jim Mattis two months earlier than had been expected, a move officials said was driven by Trump’s anger at Mattis’ resignation letter and its rebuke of his foreign policy.

On Thursday, Mattis had abruptly said he was quitting, effective Feb. 28, after falling out with Trump over his foreign policy, including surprise decisions to withdraw all troops from Syria and start planning a drawdown in Afghanistan.

Trump has come under withering criticism from fellow Republicans and international allies in recent days over his moves to wind down US involvement in Syria and Afghanistan, against the advice of his top aides and US commanders.

The exit of Mattis, highly regarded by Republicans and Democrats alike, added to their concern over what they see as Trump’s unpredictable, go-it-alone approach to global security.

In announcing his resignation, Mattis distributed a candid resignation letter addressed to Trump that laid bare the growing divide between them, and implicitly criticized Trump for failing to value America’s closest allies, who fought alongside the United States in both conflicts. Mattis said that Trump deserved to have a defense secretary more aligned with his views.

Trump made his displeasure with Mattis clear on Saturday night by tweeting that he had been “ingloriously fired” by former President Barack Obama and he had given Mattis a second chance. Obama removed Mattis as head of US Central Command in 2013.

On Sunday, Trump tweeted that Deputy Defense Secretary Patrick Shanahan would take over for Mattis on an acting basis on Jan. 1. In a tweet, Trump called the former Boeing Co executive “very talented.”

Shanahan, a longtime Boeing Co. executive, was nominated for the deputy job in early 2017.

He moved up through the management ranks at Boeing over a career that began in 1986. The Puget Sound Business Journal called him a Boeing “fix-it” man in a March 2016 report. He oversaw the company’s global supply chain strategies and use of advanced manufacturing technologies. Shanahan was central to getting the 787 Dreamliner on track after production problems in the program’s early years, the report said.

In his letter, Mattis had said he would step down at the end of February to allow for a successor to be confirmed and attend Congressional hearings and a key NATO meeting.

A senior White House official said that Trump was irked by the attention given to Mattis’ resignation letter.

“He just wants a smooth, more quick transition and felt that dragging it out for a couple of months is not good,” the official said, on condition of anonymity.

The official said Trump was expected to pick a nominee for defense secretary over the next couple of weeks.

Defense Department spokeswoman Dana White said Mattis would work with Shanahan and Pentagon leadership to ensure the department “remains focused on the defense of the nation during this transition.”

Shanahan, in his job as deputy defense secretary, has largely focused on internal Pentagon reform and issues like the creation of a Space Force.

Reuters — AP