He served during Operation Desert Storm in the 2nd Reconnaissance Battalion, and over the course of his career he was also deployed to Kosovo, Afghanistan, Haiti, and to Iraq again.

[1][9] He joined the ROTC program on the recommendation of his father to pay for college, and later decided to commission in the Marine Corps instead of the Navy.

As a field grade officer, Berger was an instructor at Marine Aviation Weapons and Tactics Squadron One in Yuma, Arizona; instructor at III Marine Expeditionary Force (MEF) Special Operations Training Group; and served on the Joint Staff as a policy planner in the Strategic Plans and Policy Directorate, J-5.

As a colonel, Berger commanded Regimental Combat Team 8 in Fallujah, Iraq, during Operation Iraqi Freedom.

[8][11] In July 2014, Berger was promoted to the rank of lieutenant general and assumed command of I Marine Expeditionary Force.

As the head of MCCDC, he began considering how the knowledge he gained while commanding Marine forces in the Pacific could be applied to the Corps.

Berger oversaw a wargame at the Naval War College that simulated a potential conflict in that region, and its results influenced his policies when he later became the commandant.

According to him, the wargame showed that mobility and sustaining forces in the Western Pacific were going to be challenges in such a conflict, but with certain changes, the Marine Corps could have an important role in sea-control and sea-denial operations.

He concluded in the document that the Corps needed major changes to align it with the 2018 National Defense Strategy, which prioritizes the strategic competition between the United States and China.

[21][25][26][24] As part of this, Force Design refocuses the Marine Corps on high-end combat, shifting away from legacy platforms like tanks and cannon artillery in favor of long-range missiles and drones.

[10][22][29][30] Politico reported that there are thirty retired Marine generals who oppose the changes brought by Force Design, including every living former Commandant, and some of them formed a dedicated group to lobby against it.

[31] Berger has defended the plan from the critics, pointing out that in "every single exercise, every war game ... the outcome in the future was not going to be good if we didn't make some kind of changes.

Brown Jr. were being considered by the White House as the two leading candidates to become the next Chairman of the Joint Chiefs of Staff when General Mark Milley retired from the post in September.