Captain Nathaniel R. Gilmer commissioned into the Marine Corps in May 2019 from the United States Naval Academy with a BS in Mechanical Engineering and attended The Basic School in June 2019 aboard Camp Barrett, VA.

In January 2021, Captain Gilmer attended the Infantry Officer's Course aboard Camp Barrett, Virginia as a student.

In April 2021, Captain Gilmer reported to Company B, 1st Battalion, 5th Marines, Camp Pendleton, California.  In May of 2021, Captain Gilmer graduated Fast Rope Master Course aboard Camp Pendleton, California.

In November 2021, Captain Gilmer deployed on the 31st Marine Expeditionary Unit as a platoon commander in Battalion Landing Team 1/5. He commanded his platoon through three certification exercises consisting of two helicopter raids and one vertical assault in support of Forward Arming and Refueling Operations. Captain Gilmer developed and supervised the 31st MEU Savage Games, a functional fitness competition.

In May 2022, Captain Gilmer transitioned to B Company Commander and Executive Officer. In October of the same year, he turned over command of the company and remained the executive officer of the same company. In April 2023, Captain Gilmer turned over responsibilities as B Co Executive Officer and became the Battalion Training Officer until July of the same year.

In August 2023, Captain Gilmer transitioned to Headquarters Company Inspector and Instructor for 25th Marine Regiment aboard Fort Devens, Massachusetts.