Defense Secretary Gen. Jim Mattis has resigned due to what appears to be irreconcilable differences with President Donald Trump.

“General Jim Mattis will be retiring, with distinction, at the end of February, after having served my Administration as Secretary of Defense for the past two years,” the president tweeted on Thursday.

“During Jim’s tenure, tremendous progress has been made, especially with respect to the purchase of new fighting … equipment. General Mattis was a great help to me in getting allies and other countries to pay their share of military obligations. A new Secretary of Defense will be named shortly. I greatly thank Jim for his service!”

There have been rumors that the two have disagreed recently, particularly over the president’s reported decision to withdraw troops from Syria.

And now there are reports that President Trump wants to pull troops out of Afghanistan, Reuters reported.

“President Donald Trump is considering significantly drawing down troops from Afghanistan, two U.S. officials told Reuters on Thursday, in the latest sign his patience is thinning both with America’s longest war and overseas military interventions, generally,” Reuters wrote.

“The U.S. officials, who spoke on condition of anonymity, said thousands of the 14,000 troops could be sent home as a result of the deliberations, the disclosure of which could undermine ongoing peace efforts with the Taliban,” it said.

The resignation letter of Gen. Mattis was tendered on Thursday and it appeared to take several shots at the president.

“Because you have a right to a Secretary of Defense whose views are better aligned with yours on these and other subjects, I believe it is right for me to step down from my position,” he said.

“My views on treating allies with respect and also being clear eyed about both malign actors and strategic competitors are strongly held and informed by over four decades of immersion in these issues,” he said.