The Pentagon’s No. 3 official has resigned after weeks of speculation on his impending departure.

John Gibson, the Department of Defense's chief management officer, submitted his resignation on Monday and will leave Nov. 30, according to a Pentagon statement released Friday. Gibson served in the role for less than nine months.

Lisa Hershman, the deputy chief management officer, will take over for Gibson in an acting capacity on Dec. 1.

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“Mr. Gibson's groundbreaking work as the first-ever DoD Chief Management Officer set conditions for the department's reform initiatives,” Pentagon spokesman Lt. Col. Joe Buccino said in the statement.

“His efforts to streamline processes, establish the department's Reform Management Group, and identify significant savings across the department will pay dividends in [fiscal 2019].”

That statement does not mention that Gibson was fired months earlier due to underperformance, according to reports.

The Wall Street Journal reported in September that Gibson was effectively forced out from his role due to a “lack of performance.”

Gibson had been asked to find savings in the Pentagon that could be redirected back into other military modernization efforts.

Defense officials told the Journal that Gibson’s duties had been diminished as White House officials looked for a replacement.

“Our commitment to bringing business reform to the department remains unwavering and will result in the increased lethality of our force,” Buccino said. “We appreciate his service to the Department and wish him continued success.”