Neller's assignments in the operating forces include: Rifle and Weapons Platoon Commander and Company Commander with Company L, 3rd Battalion, 4th Marines, 3rd Marine Division; Commanding Officer, Company A, 1st Battalion, 1st Marines; Commanding Officer, 3rd Light Armored Infantry Battalion (LAI) and Commanding Officer, 6th Marine Regiment from 10 July 1998 to 6 July 2000.[6] While with 3rd LAI he participated in Operation Restore Hope in Somalia. As the Commanding Officer, Marine Corps Security Force Company, Panama, he participated in Operations Just Cause and Promote Liberty. Additionally, he served as Executive Officer, 7th Marine Regiment, G-3, II Marine Expeditionary Force and G-3, 2nd Marine Division.[5]
Other assignments include recruit series officer, aide-de-camp and as Director of Special Training Division MCRD San Diego, California. Neller served as Student Company Executive Officer and Tactics Instructor at The Basic School, Quantico, Virginia, and in Special Projects Directorate Headquarters Marine Corps. Additionally, he served as a Staff Officer in the Policy Division of the Supreme Headquarters Allied Powers Europe in Casteau, Belgium.[5]
General officer
As a general officer, Neller has served as the Assistant Division Commander of the 2nd Marine Division and the Director, Operations Division, Plans, Policies and Operations. He was also the Deputy Commanding General (Operations), 1st Marine Expeditionary Force (Forward) during an especially dangerous time of the Iraq War from 2005 to 2007,[7] and as the Assistant Division Commander for 1st Marine Division. Neller commanded 3rd Marine Division and served as President, Marine Corps University. From January 2011 to July 2012, he served as Director for Operations, J3, The Joint Staff, Washington, D.C.[5]
Neller succeeded General Joseph Dunford as the 37th Commandant of the Marine Corps on September 24, 2015. Defense Secretary Ash Carter, who worked with Neller when he had been Director of Operations at the Joint Staff, said that Neller "is a warrior. He is a leader. He is a statesman." Him being chosen over other candidates was considered to be due to his experience of working with the Navy while being the head of Marine Forces Command, as the Marine Corps was considering a new doctrine that is based on a closer partnership with the Navy.[10]
In June 2017, General Neller told Congress that the Marine Corps is "not currently organized, trained and equipped to face a peer adversary in the year 2025."[11]