Mark Thomas Esper, President Donald Trump’s latest appointee as Secretary of Defense, will replace acting Secretary Patrick Shanahan at midnight on Sunday.

Esper, a career soldier and advisor, was Secretary of the Army before his latest appointment. He also has been a lobbyist for Raytheon, the third largest U.S. defense contractor by revenue since 2015. In 2018, 90% of Raytheon’s $25.35 billion in revenue came from military contracts.

If confirmed, Esper would succeed Jim Mattis, who resigned last December when he disagreed with the president over pulling out U.S. troops from Syria. Acting Secretary Shanahan removed his name from consideration following reports about his 2011 divorce.

Esper’s appointment comes at a critical point in deteriorating relations with Iran, after the Iranian military took down an unmanned U.S. drone last week that the country said violated its airspace. Trump authorized and then averted a military strike against Iranian targets last Thursday after assessments indicated there may be civilian casualties. The U.S. Central Command denied the airspace violation.

Had Trump allowed the planned attack on Iranian radar and missile sites, the strike likely would have been viewed as an act of war by Iran, and possibly the international community, military experts said.

Esper, 55, who was appointed Secretary of the Army in November 2017, was a West Point classmate of Secretary of State Mike Pompeo and served as an infantry officer in the 1991 Gulf War. He later commanded an airborne rifle company in Europe, and was decorated with a Bronze Star and the Legion of Merit. Afterward, Esper served in the Army Reserve and both the Virginia and District of Columbia National Guard before retiring with 21 years service in 2007.

President Trump announced Esper as acting Pentagon chief last Tuesday, calling him “a highly respected gentleman with a great career – West Point, Harvard, a tremendous talent.”

Esper graduated from West Point with a Bachelor of Science in engineering 1986. He received a Masters in public administration from the John F. Kennedy School of Government in 1995, and a Doctor of Philosophy degree from George Washington University in 2008.