"[citation needed] In British practice, regiments were commanded by their lieutenant colonels, as the colonel was a titular position[8] (with the incumbent absent from the regiment serving as a senior staff officer, a general officer, or as a member of the nobility).

Upon the outbreak of the Civil War, the rank of lieutenant colonel became much more common and was used as a "stepping stone" for officers who commanded small regiments or battalions and were expected, by default, to be promoted to full colonel once the manpower of a regiment grew in strength.

Such was the case with George A. Custer, who was a lieutenant colonel in the regular army, but held the brevet rank of major general.

In the United States Army and the United States Marine Corps (USMC), a lieutenant colonel typically commands a battalion- or squadron-sized unit (300 to 1,200 Soldiers or Marines), with a major as executive officer (XO) and a command sergeant major or sergeant major (USMC) as principal non-commissioned officer (NCO) or senior enlisted adviser (SEA).

These staff positions include G-1 (administration and personnel), G-2 (intelligence), G-3 (operations), G-4 (logistics), G-5 (planning), G-6 (computers and communications), and G-9 (Civil Affairs).

Air Force lieutenant colonels in the acquisition career fields can be selected to serve as "Materiel Leaders" (Program Managers or Branch Chiefs), similar to how other Air Force lieutenant colonels are selected to serve as squadron commanders.

In U.S. Army ROTC detachments, the commander is typically a lieutenant colonel, with several majors, captains, and non-commissioned officers serving as assistants.