(ABC NEWS) -- There's a new chief of staff in town.

Retired Gen. John Kelly was sworn in today as President Trump's most senior staffer in the White House.

Some, however, are pointing to the recent staff shakeups as a sign of turmoil in the Trump administration.

In a tweet that could be seen as a retort to critics, Trump wrote this morning, "No WH chaos!"

Kelly, the former secretary of homeland security, replaces Reince Priebus. Sean Spicer resigned as press secretary earlier this month, after Anthony Scaramucci was brought on as White House communications director. Trump has publicly criticized Attorney General Jeff Sessions while reportedly discussing in private whether to replace him.

At Kelly's swearing-in ceremony, Trump told reporters in the Oval Office, "[Kelly] will do a spectacular job, I have no doubt, as chief of staff. What he's done in terms of homeland security is record shattering."

He added, "I want to congratulate you on having done a fantastic job, general, and we look forward to — if it's possible — an even better job as chief of staff."

Kelly, 67, is a retired Marine four-star general and former head of U.S. Southern Command.

After the swearing-in, he joined a Cabinet meeting at the White House, where praise from Trump continued.