Within a division there are several brigades. Brigades are the largest units capable of mobilization in strategic sectors of the galaxy. A brigade contains two to six regiments. A brigade is the largest possible Marine Corps unit to be assigned to a starbase. Customarily a brigade is commanded by a Force Colonel, who reports to his/her division commander. Brigades can be spread out over many sectors and is responsible for supporting the regiments under its command. Brigades are named in order of creation beginning with 'first,' e.g. First Brigade (1BGD). Often regiments in a brigade are given specialized tasks to perform. A brigade is comprised of approximately 12,000 officers and troops.

A regiment is the largest possible specialized unit in the corps. Consisting of four to eight battalions, regiments are commanded by officers holding the rank of Colonel who, in turn, report to the proper brigade commanders. For the most part, regiments are specialized, each given a special task to perform within a division. A regiment is responsible for a general mission profile, while allowing each sub-unit to diversify as well. Regiments are given distinct names, based often from their origins, overall mission profile, or even their first commander, e.g. 'First Division, Third Brigade, Orion Regiment (1DIV, 3BGD, Orion REG).' Unless noted with a designator, a regiment, battalion, or company is a combat forces unit. On average, a regiment consists of approximately 3,000 officers and troops.

The largest Marine Corps unit to be assigned to a starship is a battalion. Comprised of a three to six companies, battalions are commanded by Lt. Colonels. Leading the battalion from a specialized company denoted Headquarters Company (HQ CO), the Marine Commanding Officer in charge of a battalion reports to his appropriate regiment commander. In addition to the specialization of each regiment, battalions are also given specific tasks within the larger Marine organization. Battalions assigned to starship duty are solely combat forces battalions. As with brigades, battalions are identified by their creation date, e.g. 'First Division, Third Brigade, Orion Regiment, Second Battalion (1DIV, 3BGD, Orion REG, 2BN).' Average battalions consist of approximately 500 officers and troops.

A company is the smallest unit capable of independent action in line duty. Comprised of a minimum of two platoons, three or four being the recommended number, a company is led by a Marine Captain (see Ranks for more details). Each company command reports directly to their battalion command with the exception of the Headquarters Company. The Headquarters Company consists of the battalion commander, his staff, as well as various aides, clerks, and support staff. Companies are identified with a letter from the Roman Alphabet or as Headquarters Company (HQ CO), e.g. 'First Division, Third Brigade, Romthar Regiment, Second Battalion, D Company (1DIV, 3BGD, Romthar REG, 2BN, D CO).' Average companies consists of approximately 110 officers and troops.

The smallest field command, comprised of an average of six six-man squads, is the platoon. Commanded by a First Lieutenant, a platoon command reports to the company commander with the exception of those men who serve in the Headquarters Company as support staff. A platoon in the Headquarters Company reports directly to the designated battalion command representative. Platoons are identified with a letter in the phonetic alphabet, e.g. 'First Division, Third Brigade, 2nd Andorian Regiment, Second Battalion, D Company, Platoon Echo (1DIV, 3BGD, 2nd Andorian REG, 2BN, D CO, Platoon Echo).' For the most part, a platoon consists of 40 men.

The phonetic alphabet used is as follows: Alpha Bravo Charlie Delta Echo Foxtrot Golf Hotel India Juliet Kilo Lima Mike November Oscar Papa Quebec Romeo Sierra Tango Uniform Victor Whiskey Xray Yankee Zulu.

A summary of the Marine Corps units is below.