Major Cottell graduated from Officer Candidate School and was commissioned in December 2011. In 2012, he completed The Basic School and Military Police Basic Officer Leaders Course where he received the German Armed Forces Badge for Military Proficiency.
In 2012, Major Cottell reported to Marine Wing Support Squadron 472 where he served as the Military Police Platoon Commander, and later Executive Officer of Airfield Operations Company. Major Cottell assisted in the planning and execution of the squadron's annual training exercises participating at ITX in 2013 and 2015.
In 2015, Major Cottell mobilized to Jordan and served as the Operations Officer at the United States Embassy in Amman for Marine Corps Forces Central Command (MARCENT) Coordination Element - Jordan. He was responsible for the coordination of Marine Corps assets within the host nation, and facilitated logistical requirements with senior ranking officials of the Jordanian Armed Forces. Major Cottell extended his mobilization in support of MARCENT operations in Kuwait.
Major Cottell then reported to 2nd Civil Affairs Group in Washington, D.C. where he served as Assistant Team Leader. He planned training exercises which integrated Civil Affairs capabilities and facilitated annual training requirements for the unit. In 2018, Major Cottell supported United States Marine Forces Europe (MARFOREUR)'s multi-national exercise Austere Edge in Germany.
In 2019, 2nd Civil Affairs Group was decommissioned, and redesignated as Marine Corps Advisor Company - Alpha (MCAC-A). In 2020, under the new MCAC-A command, Major Cottell mobilized with Special Purpose Marine Air-Ground Task Force (SPMAGTF) - Southern Command (SOUTHCOM) 20. He served as the Security Cooperation Team / Mobile Training Team Officer in Charge (OIC) and developed the Training and Exercise Employment Plan for his team supporting the SOUTHCOM Area of Responsibility (AOR). Major Cottell led his team to Honduras where they conducted theater security cooperation and built partner nation capacity.
In 2021, Major Cottell received orders to Training Command and served as the COVID Cell OIC. He coordinated and managed the manpower support requirements for Officer Candidate School during the COVID pandemic. Following this assignment he returned to MCAC-A as a Law Enforcement Advisor.
In 2026, Major Cottell assumed command of Support Company, 4th Law Enforcement Battalion.
Major Cottell is a graduate of the Command and Staff College Distance Education Program. He has completed the Marine Advisor Course, Civil Affairs Officer Course, and the Intermediate MAGTF Information Operations Practitioner Course.