Kevin Sweeney, the chief of staff of the US Department of Defence, has resigned his position.
Sweeney, is the third senior Pentagon official to resign after President Donald Trump’s Syria announcement, BBC Reports.
He said in a statement that “the time is right to return to the private sector”.
His resignation is coming after Donald Trump has said US forces would leave Syria.
Earlier, General Mattis quit his post after initially planning to stay in his role until February.
The former defence secretary in his resignation letter to President Trump hinted at policy differences which caused him to quit.
The letter directly to Mr Trump described the general’s views on “treating allies with respect” and using “all the tools of American power to provide for the common defence”.
“Because you have the right to have a secretary of defence 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,” Mattis wrote.
Department spokeswoman Dana White also left her post after the president’s announcement on Syria.
Kevin Sweeney, in his resignation letter said it had been an honour to serve.