Colonel Frank R. Carlin was commissioned an Infantry Officer upon graduation from Officer Candidate School Class 39-69, 9 December 1969. His first duty assignment was as Forward Observer, A Battery, 3rd Battalion, 19th Field Artillery, Fort Hood, Texas. | His subsequent assignments include: Platoon Leader, E Company, and later served as a Platoon Leader in C Company, 2nd Battalion, 1st Regiment, 196th  Brigade, 23rd Infantry Division, Vietnam; Platoon Leader, C Company, and later served as B Company Executive Officer, 1st Regiment, 114th Infantry Division, 2nd Brigade 50th AD, New Jersey; Combat Support Company Commander, B Company Commander, Battalion Signal Officer, and the Battalion S-2 (Intelligence Officer), 1st Battalion, 114th Infantry Regiment, 2nd Brigade, 50th Armored Division, Burlington, New Jersey Army National Guard: Assistant G-3 (Operations Officer) 50th Armored Division, Somerset, New Jersey; S-3 (Operations Officer) 1st Brigade, and S-3 (Operations Officer), 2nd Brigade, 50th Armored Division, Somerset, New Jersey Army National Guard; Assistant Chief of Staff, G-3 (Division Operation Officer) 50th Armored Division, Somerset, New Jersey Army National Guard; Executive Officer, 50th Brigade, 42nd Infantry Division, Fort Dix, New Jersey Army National Guard; Commander, 1st Infantry Battalion, 114th Infantry Regiment, 42nd Infantry Division, Woodbury, New Jersey Army National Guard; Chief, Training Division, Headquarters New Jersey Army National Guard; Fort Dix, New Jersey Army National Guard; Commander 254th Regiment (COMBAT ARMS), Sea Girt, New Jersey.