LtCol Nilan commissioned in 2009. As a company grade officer, LtCol Nilan served as a Fire Direction Officer, Platoon Commander and Battery Executive Officer in 3d Battalion, 10th Marines. In 2012 he deployed with the 24th MEU as a Platoon Commander. In 2013 he transferred to 2d Air Naval Gunfire Liaison Company (ANGLICO) and served as a Firepower Control Team Leader, Brigade Platoon Commander, and Assistant Operations Officer. In 2013 through 2014 he deployed to Operation Enduring Freedom. Following ANGLICO he attended Expeditionary Warfare School (EWS), and moved to 3d Battalion, 11th Marines in 2017. At 3d Battalion, 11th Marines he held the billets of Battalion Logistics Officer, Battery Commander, and Assistant Fire Support Coordinator. In 2018 he deployed with Battery M to Marine Rotational Force – Darwin.
LtCol Nilan attended Marine Corps Command and Staff College from 2019 through 2020, and then served as a Faculty Advisor at EWS from 2020 through 2022 before attending the School of Advanced Warfighting (SAW). From Summer 2023 to the Summer 2025, LtCol Nilan served with 2d Marine Logistics Command as a Plans Officer. He most recently served as the Director of 1st Marine Division Schools.