The Department of Defense's chief of staff Rear Adm. Kevin Sweeney has resigned, according to a statement.
Sweeney said in a brief statement that he planned to return to the private sector, giving no reason for his departure. His exit comes just days after Secretary of Defense James MattisJames Norman Mattis The US can't go back to business as usual with Pakistan The Hill's Morning Report - Presented by Facebook - Senate nears surprise deal on short-term debt ceiling hike Overnight Defense & National Security — Pentagon chiefs to Congress: Don't default MORE, for whom Sweeney previously served, left the agency after announcing his resignation earlier in the month.
"After two years in the Pentagon, I've decided the time is right to return to the private sector. It has been an honor to serve again alongside the men and women of the Department of Defense," Sweeney said in his announcement.
His resignation also followed that of another top Mattis ally, Pentagon spokeswoman Dana White, who announced her resignation at the end of December.
“I appreciate the opportunity afforded to me by this administration to serve alongside Secretary Mattis, our Service members and all the civilians who support them. It has been my honor and privilege,” White wrote on Twitter last month. “Stay safe and God bless.”
Mattis's resignation was thought to be tied to the surprise announcement from President TrumpDonald TrumpSenate rejects attempt to block Biden's Saudi arms sale Crenshaw slams House Freedom Caucus members as 'grifters,' 'performance artists' Senate confirms Biden's nominee to lead Customs and Border Protection MORE regarding the withdrawal of U.S. troops from Syria, where coalition forces continue to battle elements of the Islamic State in Iraq and Syria (ISIS) on the ground.
Trump's withdrawal of U.S. forces from Syria was also credited at the time with pushing the resignation of Brett McGurk, the president's top envoy to anti-ISIS coalition forces in the region.
Mattis's former deputy, Patrick ShanahanPatrick Michael ShanahanProtection of critical military benefit shows bipartisanship can work Senators introducing bill to penalize Pentagon for failed audits Overnight Defense: National Guard boosts DC presence ahead of inauguration | Lawmakers demand probes into troops' role in Capitol riot | Financial disclosures released for Biden Pentagon nominee MORE, began serving as acting Defense secretary at the beginning of January.