WASHINGTON ― Former U.S. Defense Secretary Mark Esper is joining the board of directors at Epirus, the company announced Tuesday, the latest move by the former Raytheon executive to reenter the world he left to join the Trump administration four years ago.

The venture-backed startup, based in Los Angeles, California, said in a release that adding Esper “solidifies our ability to bring to market the technology we need to help protect the U.S. warfighter and develop other new applications of our technology for broad commercial use.”

Before joining the Trump administration, Esper had been vice president of government relations for Raytheon from 2010 to 2017. Raytheon is now the fifth-largest defense contractor in the world, according to the latest Defense News Top 100 list.

A former Army lieutenant colonel, Esper was a longtime congressional staffer and served as a lead national security adviser for then-Senate Majority Leader Bill Frist. As Army secretary under President Donald Trump in 2018 and early 2019, and later as defense secretary, Esper was known for a “night court” budgeting process that took a hard look at legacy department programs and cut a number of them, refocusing funds on efforts to challenge China and Russia.

Fired by Trump in the days following the 2020 presidential election, Esper was then the third man to exit the top job at the Pentagon under the administration, following Jim Mattis and, in an acting capacity, Patrick Shanahan.

Epirus, which launched in 2018, last year inked a strategic supplier agreement with Northrop Grumman in which the latter would receive exclusive access to the former’s software-defined electromagnetic pulse system, Leonidas. The system is part of a $2 billion counter-drone market, which is expected to continue growing as commercial drones become cheaper and more commonplace, posing an asymmetric threat on the battlefield as well as a threat to airports, sports stadiums, government buildings and urban areas.

So many companies are in the field that the Pentagon is working to streamline the number of counter-drone platforms available across the department.

In a statement, Esper said his career move will serve as a continuation of his work to address emerging threats.

“At a time when new, low-cost technologies can empower our adversaries and make anyone a target, America must stay ahead of its rivals as we modernize and protect our national security interests for years to come,” Esper said. “Epirus stands at the vanguard of those accelerating military and homeland security applications of game-changing technology to disarm drones used to launch lethal attacks against our service members and civilians anytime, anywhere.”

Epirus CEO Leigh Madden was general manager for Microsoft’s national security business before he joined the firm, and its chief financial officer, Ken Bedingfield, is a former chief financial officer at Northrop. The former chairman of Epirus is Joe Lonsdale, co-founder of the Silicon Valley data-analytics company Palantir Technologies.

In addition to the Epirus role, Esper joined the McCain Institute for International Leadership in March as its first John S. McCain distinguished fellow. He is also a member of the Atlantic Council’s board of directors.