MARINE ORGANISATION

It has long been said that the Marines deploy as brigades but fight as divisions. The five brigades formed just prior to, during, and immediately after the war were tied directly to specific divisions. They were raised for a specific purpose, usually a rapid deployment. Only one saw combat and in itself became a division. The division was the basic combat formation assigned the task of executing major amphibious assaults and securing island objectives.

The largest permanent Marine formations prior to early 1941 were the 1st and 2nd Marine Brigades, formed on the East and West Coasts in 1935–36. Each brigade was built around an infantry regiment and an aircraft group, but all units were nevertheless under strength. If deployed for combat, it was planned to supplement them with ships’ guards. Initially, the Fleet Marine Force (FMF) was oriented principally toward the Atlantic and Caribbean; the Pacific at that time was of secondary importance. From 1940–41 German submarines were the major threat, and the fear that Germany might occupy French possessions in the Caribbean and possibly attack the Azores. It was not until the summer of 1941 that the FMF began to focus its attention more on the Pacific. By that time the entire 15,000-man Marine Corps Reserve had been mobilised and the Marine Corps itself consisted of some 50,000 troops, though its units were still largely under strength.

A 1st MarDiv weapons platoon, armed with M1919A4 machine guns, undertakes landing training on Chesapeake Bay in early 1942. At this time the Marines were still planning to participate in the invasion of North Africa alongside the Army. (Shelby Stanton collection)

Marine division organisation

The forming of Marine divisions was proposed in 1940. The new 1st and 2nd Marine Divisions (MarDiv) were formed in early 1941 by converting the two permanent brigades. They were slow in developing, and it was not until mid-1942 that they were considered ready for deployment. By then they had matured into a standard structure with sufficiently diverse units to make them self-contained amphibious fighting forces well suited for combat on rugged tropical islands.

Several changes were introduced each year of the war to capitalise on lessons learned from previous operations, to adapt to expected Japanese resistance, increase firepower, reduce manpower needs, provide for more effective allocation of resources between divisions and corps, and to further streamline divisional logistics. The few units deleted from the division were reassigned to the FMF. (Unlike the Army’s divisions, which have endured many and varied reorganisations, today’s Marine division bears a striking resemblance to its World War II predecessor. Even the assignment of regiments has changed little.) In 1941 each division consisted of a division headquarters; service, medical, engineer, light tank and parachute battalions; scout, anti-aircraft machine gun, signal, chemical, guard and motor transport companies; two infantry regiments; and an artillery regiment.

Ongoing fleet landing exercises identified numerous flaws in unit organisation, equipment, logistical support and tactics. As a result a pioneer battalion was added, to provide manpower for moving supplies from landing beaches to combat units. This new unit, along with the existing engineer battalion, and an attached naval construction battalion were placed in a new engineer regiment. A headquarters battalion was formed to consolidate divisional command and to control the various elements. The anti-aircraft company was absorbed into a new special weapons battalion, along with new antitank sub-units. A third infantry regiment was added, along with amphibian tractor, service, and medical battalions, while the chemical company was deleted. The concept of ‘triangular reinforcement’ was strictly adhered to by the Marines. Divisional combat support and service units were organised for attachment to the three regiments and this concept was applied at all lower levels. The division headquarters battalion had headquarters, signal and military police companies. A reconnaissance company was added in 1944.

The infantry regiment was the core of the division’s fighting force. While its basic organisation changed little over the war years, its allocation of manpower and weapons did, and it underwent refinements in sub-unit organisation. Command and control, and minimal service support was provided by a headquarters and service company. A regimental weapons company had three 37 mm gun platoons (4×37 mm AT; 20 mm AA/AT guns prior to 1943) and a 75 mm gun platoon (2×75 mm M3 self-propelled AT guns, 4 in 1944).

Each of the three infantry battalions had a headquarters company, three rifle companies, and a weapons company (until 1944). The rifle companies had a large headquarters element, three rifle platoons and a weapons platoon, which after May 1944 was replaced by a machine gun platoon. Rifle platoons numbered between 42 and 46 men. The platoon headquarters had a 2nd lieutenant platoon leader, platoon sergeant, and five radio operators and messengers. Prior to 1944 they had three nine-man rifle squads consisting of a squad leader (sergeant), assistant squad leader (corporal), two scouts, three riflemen (all armed with M1 rifles), a grenadier (M1 rifle, M7 rifle grenade launcher or, prior to 1943, M1903 rifle, M1 grenade launcher), and an automatic rifle man (M1918A2BAR). The automatic rifle squad had a squad leader (M50 sub-machine gun), two automatic riflemen, and five riflemen. From April 1943, some riflemen were redesignated assistant automatic riflemen and armed with M1 carbines.

However, there was an alternative squad organisation in the works. Early in the 1927–33 Nicaraguan Campaign Lt. Merritt Edson of the 5th Marines had developed the technique of dividing rifle units into three- and four-man ‘fighting groups’ centred around an automatic weapon. This had proved extremely successful for jungle patrols. Later, when Major Edson and other 4th Marines officers examined the concept, by then known as ‘fighting teams’, in China in the late 1930s, and the 1st and 2nd Raider Battalions (Lt.Col. Edson commanded the 1st) organised their squads under this concept in 1941. It was also tried out by the 22nd Marines at Eniwetok in early 1944, and was credited with enabling small-unit leaders to continue their missions when communication was lost and the unit was under heavy fire. The new 4th Marines, formed from the raider battalions, continued the technique. Reports by these and other units led the headquarters of the Marine Corps to test the concept seriously in the States using the 24th Marines. By the end of March 1944 the rifle company table of organisation had been changed to reflect the use of four-man ‘fire teams’ and the automatic rifle squad was dissolved.

The new rifle squad organisation called for a squad leader (sergeant; M1 carbine) leading three fire teams composed of a team leader (corporal; M1 rifle, M7 grenade launcher), rifleman (M1 rifle, M7 grenade launcher), automatic rifleman (M1918A2 BAR) and assistant automatic rifleman (M1 carbine). The four-man fire teams allowed the triangular organisation concept to be maintained down to the smallest tactical entity, with every commander or leader controlling three manoeuvre elements, be it regiments, battalions, companies, platoons, squads, teams or men. Additionally, 27 each of 2.36 in. bazookas, flamethrowers and demolition kits – one per rifle squad – were pooled in the battalion headquarters.

The rifle company’s weapons platoon had a small headquarters as well as machine gun and mortar sections. To begin with they had two .30-cal. M1919A4 light machine guns and two 60 mm mortars. This was increased to five machine guns and three mortars in April 1943. The weapons platoon was redesignated a machine gun platoon in May 1944, with six M1919A4 light and six M1917A1 heavy machine guns; the latter transferred from the by then disbanded battalion weapons company. The weapons platoon’s 60 mm mortar section was transferred to the company headquarters.

The battalion weapons company began with an anti-aircraft and anti-tank gun platoon (4×20 mm AA/AT), mortar platoon (4×81 mm) and three machine gun platoons (8×M1917A1 each). In April 1943 the anti-tank platoon was deleted and the machine gun platoons were reduced to four M1917A1s each. The battalion weapons company was dissolved in May 1944, with the three machine gun platoons’ assets transferred to the rifle companies and the 81 mm mortar platoon moved to the battalion headquarters company.

The May 1944 reorganisation (i.e. deletion of the battalion weapons company and rifle company weapons platoon, reallocation of crew-served weapons to the more immediate user level, and institution of the fire team) allowed for more effective combat organisation, efficient weapons employment and tactical teamwork. (The reorganisation had been announced in January 1944 and the 2nd and 4th MarDivs soon began reorganising. They completed it in May and assaulted Saipan in June. The other divisions were reorganised in time for their subsequent operations.)

1st MarDiv Marines embark a troop train bound for the West Coast, 1942. They wear khakis, without leggings, new M1 steel helmets, and M1941 field gear in the field transport pack configuration.

The Marines occasionally utilised separate infantry regiments for special deployments. These included the 3rd, 4th, 9th, 21st, 22nd and 24th Marines (Reinforced), either detached from divisions or as actual separate units. They were usually reinforced with a 75 mm pack howitzer battalion and tank, engineer, pioneer, signal, motor transport, and medical companies plus service detachments to make them self-sufficient.

The artillery regiment went through several reorganisations that changed the number of battalions and the calibres of assigned weapons. Prior to 1943 there were three 75 mm howitzer battalions and one of 105 mm. This was changed to three 75 mm and two 105 mm battalions in April 1943. In May 1944 one 75 mm battalion was converted to 165 mm. In late 1945 the 75 mm pack howitzers were with-drawn, leaving one 155 mm and three 105 mm howitzer battalions. The 105 mm batteries had four pieces, until 1943 when they received two more, while the 75 mm batteries had six from the beginning. The regiment and battalions each had a headquarters and service battery.

Marines debark from a troop train while being transferred from the East to West Coast, 1942. All wear forest green winter service uniforms and are armed with the M1903 Springfield. (Shelby Stanton collection)

The engineer regiments possessed engineer, pioneer and naval construction battalions, each with a headquarters and three ‘line’ companies. While officially dissolved in May 1944, the 2nd, 3rd, and 4th MarDivs had embarked for combat operations prior to this, and their regiments were retained at least through August.

The old division tank companies were redesignated scout companies in early 1941. They had 14 M3A1 scout cars and motorcycles. The companies were incorporated into the new light tank battalions raised in late 1941, but retained their original designations – 1st and 2nd. The four tank companies had 18 M3-scries tanks (three platoons of five and three in the headquarters). The scout cars and motorcycles were never employed in combat; the scout companies normally patrolled on foot. In April 1943 battalions lost a company to newly forming divisions and the scouts were usually redesignated Company D. In May 1944 the battalions were authorised M4-series tanks and ‘light’ was dropped from their designation. Each company had 15 tanks – four per platoon and three in the headquarters. The battalions were not immediately and completely re-equipped with medium tanks. Some were committed to combat with one or two medium tank companies and the rest were equipped with light tanks. At the same time, the scout companies were redesignated reconnaissance, assigned their parent division’s number, and reassigned to the division headquarters battalion.

The special weapons battalion originally had two anti-aircraft artillery batteries (one with 16×40 mm, the other with 6×90 mm guns) and three anti-tank batteries (each with 6×37 mm and 2×75 mm self-propelled AT guns). In April 1943 the 90 mm battery was deleted. The battalion was dissolved in May 1944; the 75 mm self-propelled guns were reassigned to regimental weapons companies, and the 40 mm guns to the new anti-aircraft battalions.

Troops of the 1st Raider Battalion practise landing from a Landing Craft, Rubber (Large) (LCR(L)) at Camp Lejeune, N.C. The foremost raider carries a Reising M50 submachine gun.

Marine raiders cross a bridge constructed of linked toggle ropes, a technique borrowed from the British Commandos. Carried by each raider, these consisted of an 8 ft. rope with a loop on one end and a wood handle on the other. Outfitted in camouflage utilities, they are armed with M1903 rifles. (Shelby Stanton collection)

Divisional service troops had three types of battalions. The service battalion originally had headquarters, service and supply, ordnance, one division and three regimental transport companies. In 1943 a motor transport battalion was added and the transport companies were transferred to it and restructured into three companies. The medical battalion’s five companies were manned mainly by Navy medical personnel (surgeons, dentists, corpsmen and technicians), but something over one-fifth of its strength was Marine support personnel. From late 1943 to 1945 the 1st to 4th MarDivs consolidated their division headquarters and service battalions into a single headquarters and service battalion.

The amphibian tractor battalion, a component of the service troops, had 100 standard amtracs and 59 support amtracs divided between its headquarters and service company and three tractor companies. In 1943 the number of support amtracs was increased to 73. The battalion was removed from the division in 1944, but that did not signal the end of organic amtracs, since engineer, pioneer, and motor transport battalions were still equipped with a total of 71 specialised support amtracs.

Fleet Marine Force units

The FMF possessed a pool of combat support and service units for attachment to amphibious corps and Marine divisions, or for special employment. The principal units are discussed here; others are addressed in the Marine Units section.

Each 503-man parachute battalion was originally composed of a headquarters company and companies A, B, and C. When the 1st Parachute Regiment was formed in 1943, the companies were redesignated in sequence through the regiment’s battalions: 1st – A, B, C; 2nd – E, F, G; 3rd – I, K, L; and 4th – N, O, P. Companies D, H, M and Q were reserved, in the event of battalion weapons companies being authorised. The rifle companies had three rifle platoons, each armed with a 2.36 in. bazooka, a 60 mm mortar, and three M1941 light machine guns. The Regiment possessed a headquarters and service company and a weapons company.

Artillery men practise loading a 75 mm M1A1 pack howitzer aboard a Landing Craft, Vehicle, Personnel (LCVP) at New River, N.C. They wear their M1941 gear in the field marching pack configuration.

Prior to the formation of the 1st Raider Regiment in 1943, battalions had a weapons company and four rifle companies designated A, B, C, D (rifle) and E (weapons). For a time the 2nd Raider Battalion had companies A to F (all rifle). The 4th Raider Battalion initially had only companies A to C (rifle) and D (weapons); between December 1942 and February 1943 it had companies A to D (rifle), E (demolitions) and F (engineer); it was then reorganised as the other battalions. Upon formation of the 1st Raider Regiment, the battalions were reorganised with a weapons company and three rifle companies, designated in sequence through the regiment: 1st – A, B, C, D; 2nd – E, F, G, H; 3rd – I, K, L, M; and 4th – N, O, P, Q. Companies H, M and Q were weapons. This system remained in effect even when the 2nd and 3rd Raider Battalions were attached to the 2nd Raider Regiment (Provisional). The rifle companies had a weapons and three rifle platoons each with three nine-man squads. The weapons platoon had two each of M1919A4 machine guns, .55-cal. anti-tank rifles and 60 mm mortars. The weapons company had a demolitions (2× .55-cal. AT rifles), a mortar (3×60 mm) and two machine gun (4×M1919A4) platoons.

‘Paramarines’ await the green light aboard an R4D-1 (same as Army Air Forces C-47), 1942. This sergeant wears forest green on khaki chevrons on sage green parachutist coveralls. His headgear is a seal brown leather A-7 summer flying helmet.

The defence battalions’ structure varied a great deal, since they were organised to perform specific missions (in the early days they were often split between islands, and detachments from one battalion could reinforce another), and it was not uncommon for additional provisional batteries to be formed. The 6th Defense Battalion (Reinforced) on Midway Island in June 1942 had a total of seven coast defence and eight anti-aircraft batteries. The battalions were virtually of regimental size. From 1939 to 1943 they generally consisted of a coast defence group with three coast defence gun batteries (usually 5 in. guns), an anti-aircraft group with a searchlight and three anti-aircraft gun batteries (4×3 in. AA guns), and a machine gun group with two batteries (one with .50-cal. water-cooled for AA, the other with M1917A1s for beach defence). From 1943 to 1944 they had a 155 mm artillery group with two batteries (4×155 mm guns), a 90 mm anti-aircraft group with a searchlight and four gun batteries (4×90 mm), and a special weapons group (sometimes referred to as a light antiaircraft group) with three batteries (two with 18×40 mm, one with 18×20 mm). The battalion and groups each had headquarters and service batteries, and there was usually a light tank platoon. The battalions were also equipped with SCR-268 early warning radars and sound locators.

A Marine parachutist prepares to board his aircraft wearing an M1 steel helmet, without a liner, over a seal brown leather A-7 summer flying helmet with sage green parachutist coveralls. He is outfitted with a Navy NAF 68514 troop parachute.

The defence battalions were converted to antiaircraft artillery battalions between April and September 1944, and their artillery groups formed the core of new artillery battalions. The AAA battalions consisted of heavy and light AAA groups; the former had three batteries of 90 mm guns and the latter had three of 40 mm guns, plus a searchlight battery.

The artillery battalions, formed during 1944, had a headquarters and service battery, and three 155 mm howitzer or gun batteries with four pieces each. The 4th Artillery Battalion was equipped with 105 mm howitzers until early 1945.

Organisation for combat

When task organised for combat, Marine divisions attached combat support and service units down to regimental, battalion and even company level. Typical attachments from the FMF to a division for an assault landing included a war dog platoon, signal intelligence platoon (radio direction finding), provisional rocket detachment (4.5 in. barrage rockets), joint assault signal company (Navy, Marine and Army personnel coordinating naval gunfire, artillery and air support), and amphibian truck company (Ducks), all of which were incorporated in the division after the war. Various artillery, defence and amphibian tractor battalions were also attached, as and when the operation required. Task organised and reinforced regiments were initially called ‘combat groups’, and their reinforced battalions were called ‘combat teams’. In late 1943 these were redesignated ‘regimental landing teams’ and ‘battalion landing teams’ respectively.

Navy Construction Battalion (CB, or ‘Seabees’) personnel at Camp Peary, Va., debark from 30 ft. rampless Landing Craft, Personnels with bangalor torpedoes and demolition materials. The Seabee insignia is painted on the LCP’s bow. The M1903 rifle armed Seabees wear M1 helmets, one-piece mechanic’s coveralls, and leggings.

For the August 1943 landing on Guadalcanal, the 1st MarDiv formed Combat Groups A (5th Marines) and B (1st Marines). The groups consisted of an infantry regiment, an artillery battalion, one each of tank, engineer, pioneer, amphibian tractor and medical companies, and one each of scout, special weapons and transport platoons. Combat Group A’s infantry battalions were designated combat teams 1, 2 and 3, while Combat Group B’s were called Combat Teams 4, 5 and 6. Each combat team consisted of an infantry battalion, a 75 mm pack howitzer battery, and engineer, pioneer and amphibian tractor platoons, plus small service elements. A division support group was also formed, comprising four subgroups of artillery, special weapons, engineer, pioneer, amphibian tractor, headquarters, communications, and medical elements, plus the 1st Parachute Battalion. The division was not only organised to land and fight under this structure, but also embarked its transport as groups and teams.

The use of regimental landing teams (RLTs) and battalion landing teams (BLTs) was first undertaken by the 2nd MarDiv at Tarawa (Betio) in November 1943. The first two regiments to land were organised as RLTs 2 and 8 (bearing the designation of their parent regiment), reinforced by a 105 mm artillery battalion and various combat support units. The BLTs were designated Red, White and Blue for 1st, 2nd and 3rd Battalions respectively, and reinforced by a 75 mm pack howitzer battalion, tank company and engineer platoon. The BLTs possessed only combat elements; all service elements supported the RLTs and the division.

A 3rd Defense Battalion twin 20 mm Mk IV anti-aircraft gun, mounted on a former 37 mm M1 gun M3A1 mount, protects the Marine beachhead on Guadalcanal. The 20 mm had a maximum range of 5,500 yards.

Battalions and companies also task organised their assets to counter enemy capabilities more effectively. In early 1944 the 4th MarDiv organised its assault companies into ‘assault and demolition teams’ for the Roi-Namur landing. Companies formed six teams, each led by an officer and consisting of a four-man light machine gun group, a five-man demolitions group, a three-man bazooka group and a four-man support group (two BARs). A team was carried in an LVT(2) amtrac. The follow-on reserve companies formed ‘boat teams’ which were similar and were carried in an LCVP landing craft; the boat teams lacked the machine gun group.

Armed with M1903 rifles fitted with M1905 bayonets, a 1st MarDiv squad searches an abandoned enemy shelter in the Solomons, 1942. (Shelby Stanton collection)

There was no fixed organisation for Marine brigades. They were established as provisional formations to accomplish specific missions, and most of their assets would be drawn from the same division. Brigades generally consisted of one or two infantry regiments, an artillery and/or a defence battalion, and small combat support and service elements. Upon disbandment, the brigades’ units would be returned to their parent division’s control. Wartime brigades were designated 1st, 2nd and 3rd. A 1st Brigade was formed immediately before and during the war, and a 3rd Brigade was formed during and immediately after the war. However, despite using the same name, the later 1st and 3rd brigades carried separate lineages to the earlier ones.

More commonly known as ‘Seabees’, derived from ‘CB’ for Construction Battalions.

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