WASHINGTON — The Pentagon’s top two technology experts have submitted their resignations.

Mike Griffin, who became the Defense Department’s first undersecretary of research and engineering in early 2018, and his deputy Lisa Porter have both submitted their resignations, a defense official confirmed to Defense News. The two will be exiting the building July 10.

In a letter to R&E staff, Griffin and Porter wrote that “a private-sector opportunity has presented itself to us, offering an opportunity we have decided to pursue together.”

“It has been a pleasure leading this great team over the past few years. We greatly appreciate your hard work, diligence, integrity, and devotion to technical excellence and technical truth in furtherance of the R&E mission,” the duo wrote. “We wish you all the very best.”

They become the third and fourth officials to submit resignations in the last week. On June 16, Elaine McCusker, the department’s acting comptroller, submitted her resignation, followed two days later by Kathryn Wheelbarger, the acting assistant defense secretary for international security affairs.

News of Griffin and Porter’s resignations were first reported by Inside Defense.

In his role as R&E head, Griffin had the lead on developing new capabilities for the department, such as hypersonic weapons, directed energy and a variety of space-based programs. Included in his portfolio were the Missile Defense Agency and the Defense Advanced Research Projects Agency.

Porter, who previously was executive vice president and director of In-Q-Tel Labs, served as Griffin’s deputy from 2018 onward. Although highly respected, she kept a low profile, largely avoiding media engagements during her time in office.

A former NASA head under President George W. Bush, Griffin entered the Department of Defense with a reputation as an innovative thinker, but also as someone who could be prickly with others. In his first public speech after taking office, he infamously bragged that he answered to no one but the secretary and deputy secretary of defense — a statement that rankled members of Congress.

At the DoD, Griffin showed a strong personality that clashed with various service-level executives, with the most public fight coming with former Air Force Secretary Heather Wilson. The news emerged a day after the House Armed Services Committee recommended removing the Missile Defense Agency from under Griffin’s control.

Members of Congress have expressed frustration with Griffin’s decision to cancel the Redesigned Kill Vehicle. Alaska Republican Sen. Dan Sullivan said the move would mean 20 missile silos at Fort Greeley will be empty for a decade, and meant Griffin was out of step with the president.

“Heck, if you were at the Pentagon when the president was announcing the Missile Defense Review, he specifically mentioned these silos at Fort Greeley. I’m not even sure he knows about the fact that one of his lower-level undersecretaries decided on his own to dig 20 holes and not put anything in there for at least 10 years,” Sullivan, a member of the Senate Armed Services Committee, told Defense News last month. “That just makes no sense. None. Zero.”

Griffin himself may have hinted that his time at the building is coming to a close in a May 20 speech, which he opened by noting that being a “presidential appointee, I think most of you know, is literally at the pleasure of the administration. So, we never know for employment is until tomorrow or next year or anything in between.

“But, that’s okay. You don’t you don’t take these jobs unless you understand that. This is my third time in that arena,” he said.

This is a developing story. Stay tuned for updates.