Washington (CNN) Retired Adm. William "Bill" McRaven resigned from the Pentagon's Defense Innovation Board last month, just days after issuing a stunning rebuke of President Donald Trump's decision to revoke the security clearance of former CIA Director John Brennan, the Pentagon confirmed Thursday.

"I can confirm that Admiral (ret) William H. McRaven resigned from the Defense Innovation Board, effective August 20, 2018," Pentagon spokesperson Heather Babb told CNN in a statement. "The Department appreciates his service and contribution on the board."

The Defense Innovation Board serves as an independent advisory committee to the Pentagon specializing in issues related to technology and innovation. McRaven's picture has been removed from the board's website.

While his departure was first reported by Defense News on Thursday, the Pentagon confirmed that McRaven, the former head of Special Operations Command, officially resigned last month, just four days after he authored a blistering op-ed in The Washington Post slamming Trump's decision to revoke Brennan's clearance.

"Through your actions, you have embarrassed us in the eyes of our children, humiliated us on the world stage and, worst of all, divided us as a nation," McRaven said of Trump's unprecedented use of a presidential authority over the classification system to strike back at one of his prominent critics.

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