Lieutenant Colonel Steven E. Alsop was commissioned in the United States Marine Corps through the platoon leaders course in 2004. After graduating from The Basic School and Infantry Officer Course in 2005, he was assigned to 1st Battalion, 1st Marines where he served as a Rifle Platoon Commander, and Weapons Company Executive Officer, deploying twice to Operation Iraqi Freedom.

Lieutenant Colonel Alsop was then assigned to various units in III MEF, Okinawa Japan where he served as Air Officer and Force detachment Executive Officer participating in frequent exercises and training events throughout US Forces Pacific and US Forces Korea. Lieutenant Colonel Alsop was then assigned to Marine Corps Detachment, Ft Benning, Georgia as a Liaison Officer. 

In 2010 Lieutenant Colonel Alsop reported to 3d Battalion, 2d Marines and deployed as a combat replacement to 1st Battalion, 2d Marines and Operation Enduring Freedom. Lieutenant Colonel Alsop rejoined 3d Battalion, 2d Marines and deployed to Afghanistan as Weapons Company Commander. Upon completion Lieutenant Colonel Alsop redeployed back to Operation Enduring Freedom as a member of a Police Advisor Team.

In 2013 Lieutenant Colonel Alsop was transferred to 3d Force Reconnaissance Company, where he served as Inspector-Instructor. In 2016 Lieutenant Colonel Alsop was transferred to Air Command and Staff College as a resident student.

In 2017 Lieutenant Colonel Alsop transferred to 2d Reconnaissance Battalion where he served as Battalion Operations Officer and Battalion Executive Officer.

In 2019 Lieutenant Colonel Alsop transferred to Air Command and Staff College and served as a War theory and Joint Planning Process instructor. In 2024 he assumed command of the Marine Corps Detachment, Ft Moore, GA.

Lieutenant Colonel Alsop is a graduate of the US Army Maneuver Captain's Career Course, and U.S. Air Force Air Command and Staff College. His personal decorations include the Bronze Star, Purple Heart, Meritorious Service Medal x2, and Combat Action Ribbon x2.