The approximate size of various Army units (numbers vary based on type of unit, such as artillery or infantry):
Squad: As many as 12 soldiers; led by a sergeant.
Platoon: Three or four squads. Led by a second lieutenant.
Company: Three or four platoons; generally up to 200 soldiers. Commanded by a captain.
Battalion: Five or six companies plus support elements, such as mortar, scout and supply platoons; generally up to 800 soldiers. Commanded by a lieutenant colonel.
Brigade: Three to six battalions; generally up to 5,000 soldiers. Commanded by a full colonel or a brigadier (one-star) general, depending on size and whether the unit operates independently.
Division: Three to six brigades; generally 10,000 to 20,000 soldiers. Commanded by at least a major (two-star) general.
Corps: Two to four divisions plus many specialized units, such as engineer and military intelligence brigades. Commanded by at least a lieutenant (three-star) general. This is generally the largest single command in the Army.
(c) 2003, Knight Ridder/Tribune Information Services.