President Donald Trump tweeted Monday congratulations to White House chief of staff John Kelly for marking his first year in the position.

"Congratulations to Gen. John Kelly," the president said in the post. "Today we celebrate his first full year as White House chief of staff."

Kelly, 68, a retired Marine Corps general, was Homeland Security chief when Trump named him to succeed Reince Priebus, who had resigned.

But Kelly has had a tumultuous year in the position, facing numerous reports he had threatened to resign — including one last month that Trump had even spoken with advisers about a possible replacement — and that he had privately called Trump and "idiot," which he denied.

In March, reports disclosed Trump had been relying less on Kelly to make decisions and has not included him on phone conversations with foreign heads of state.

During Kelly's tenure, he has fired several White House staffers, including former Communications Director Anthony Scaramucci and aide Omarosa Manigault Newman — and he advised Trump to dismiss embattled EPA Administrator Scott Pruitt before he quit earlier this month.

In addition, Kelly warned two key administration officials, Secretary of State Rex Tillerson and Veterans Affairs Secretary David Shulkin, they would be fired before President Trump announced it on Twitter.

The president, still, has consistently defended Kelly, often taking to Twitter to declare he is "doing a fantastic job" and showering other praise.