Mark Esper is the new acting Defense Secretary

Acting Defense Secretary Mark Esper arrives at the Pentagon in Washington, June 24, 2019. Esper has been in politics for some time. He's worked under Senate Majority Leader Bill Frist, the House Armed Services Committee, the Senate Foreign Relations Committee, and the Senate Government Affairs Committee (now Senate Homeland Security and Governmental Affairs). Esper also worked for Senator Chuck Hagel, who served as President Barack Obama's Defense Secretary.

Acting Defense Secretary Mark Esper arrives at the Pentagon in Washington, Monday, June 24, 2019. Esper holds a doctorate in public policy from George Washington University, where he completed his dissertationin 2008 titled "The role of Congress in the development of the United States' strategic nuclear forces, 1947–1968." Esper completed a Masters of Public Administration from Harvard in 1995. He graduated from the U.S. Military Academy in 1986.

First Lady Melania Trump and Karen Pence, Vice President Mike Pence's wife, speak alongside Secretary of the Army Mark Esper as they visit troops and their families in Fort Bragg, N.C., April 15, 2019.

First Lady Melania Trump and Karen Pence, Vice President Mike Pence's wife, speak alongside Secretary of the Army Mark Esper as they visit troops and their families in Fort Bragg, N.C.,  April 15, 2019.

President Donald Trump, Secretary of State Mike Pompeo, acting Secretary of Defense Patrick Shanahan, Secretary of the Army Mark Esper, Director of the Defense Intelligence Agency Lt. Gen. Robert Ashley, and Col. Dawn C. Lancaster, Commander Air Force Mortuary Affairs, and other members of the official party watch as they transfer the remains of Scott A. Wirtz, at Dover Air Force Base, Jan. 19, 2019. According to the Department of Defense, Wirtz, a civilian and former Navy SEAL from St. Louis, Mo., was killed Jan.16, 2019, in a suicide bomb attack in Manbij, Syria.

Secratary of the Army, Mark Esper enters Michie Stadium for the 221st graduation and commissioning ceremony at the United States Military Academy at West Point, May 25, 2019. Cadets graduate and are commissioned as Army 2nd lieutenants.

Incoming Acting Secretary of Defense Mark Esper greets Outgoing Acting Secretary of Defense, Patrick Shanahan, as Shanahan is honored during a Clap Out farewell ceremony by Pentagon employees gathered on the steps on his last day at the Pentagon on June 21, 2019 in Arlington, Va.

Army secretary Mark Esper poses for a photo with quarterback Kelvin Hopkins Jr. during the second half of Armed Forces Bowl NCAA college football game against Houston Dec. 22, 2018, in Fort Worth, Texas. Army won 70-14.

Acting Defense Secretary Mark Esper arrives at the Pentagon in Washington, June 24, 2019.

Secretary of the Army Mark Esper speaks during a House Armed Services Committee budget hearing on Capitol Hill in Washington, April 2, 2019.

Secretary of the Army Mark Esper throws out a ceremonial first pitch before a baseball game between the Washington Nationals and the San Francisco Giants at Nationals Park,  June 10, 2018, in Washington.

Acting Secretary of Defense Mark Esper, center, and others applaud during the farewell ceremony for outgoing acting Secretary of Defense Patrick Shanahan at the Pentagon, June 21, 2019 in Washington.

Secretary of the Army Mark Esper places a flag at the gravesite of a fallen soldier as members of the Army 3d U.S. Infantry Regiment, The Old Guard, honor the nation's fallen military heroes during its annual Flags In ceremony at Arlington National Cemetery, May 24, 2018, in Arlington, Va.

Army Undersecretary Ryan McCarthy, Army Secretary Mark Esper, Army Chief of Staff Gen. Mark Milley and Army Vice Chief of Staff Gen. James McConville announce that Austin, Texas, will be the new headquarters for the Army Futures Command during a news conference at the Pentagon July 13, 2018 in Arlington, Virginia. The Army is undergoing its biggest reorganization in 45 years with the creation of the Army Futures Command, which is tasked with modernizing the fighting force.

Secretary of the Army Mark Esper speaks to reporters in his office at the Pentagon on Sept. 19, 2018 in Washington, D

Secretary of the Army Mark Esper, right, presents the game ball to referee Luke Richmond during the opening ceremonies of the Armed Forces Bowl NCAA college football game between Houston and Army,  Dec. 22, 2018, in Fort Worth, Texas.