Former Defense Secretary Jim Mattis is returning to his previous role with the Hoover Institution — a think tank located on Stanford University’s campus.

Mattis will be researching and writing about domestic and international security policy, as well as participating in military and national security events in California and Washington, the think tank said in a press release Tuesday.

“I have long relied on the work of Hoover to supplement my understanding of the critical challenges facing our country and to help guide tough decisions," Mattis said in the press release. “I believe we have an obligation to pass on the lessons we’ve learned so that future generations can study, learn and become better. Hoover has made this part of its mission, and I look forward to returning.”

Mattis will serve as the Davies Family Distinguished Fellow at the Hoover Institution. He previously served as the Davies Family Distinguished Visiting Fellow until being confirmed as the 26th secretary of defense in January 2017.

“The wealth of knowledge and experience of an already extraordinary career has been made even richer by General Mattis’ latest endeavor as secretary of defense, and we are fortunate to once again be beneficiaries of his acumen," said Tom Gilligan, director of the Hoover Institution.

“One can find no one more universally respected for his honor, character, and relentless commitment to safeguarding American ideals than Jim Mattis.”

Trump claims he coined the nickname ‘Mad Dog’ Mattis Mattis — who preferred the call sign "Chaos" — has been fighting the "Mad Dog" moniker for at least 15 years.

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Mattis completed a 43-year career as an infantry Marine, in addition to his tenure as a DoD civilian.

He led an assault battalion in Operation Desert Storm, commanded troops against the Taliban in southern Afghanistan and served during the invasion of Iraq and subsequent stability operations.

Mattis commanded U.S. Joint Forces Command, NATO’s Supreme Allied Command for Transformation and U.S. Central Command as a general. He was succeeded in his role of leading the Pentagon by Acting Defense Secretary Patrick Shanahan.