The Interwar Years and World War II
In between wars
In seeking to reduce military expenditures between 1921 and 1941, the U.S. government demobilized (most) of its armed forces. Although somewhat reduced in size following the First World War, the Marine Corps served as an intervention force during the so-called Banana Wars. While roundly criticized by anti-Imperialists, the Banana Wars nevertheless prepared Marines for the advent of World War II. Had it not been for those interventions, there would have been no “seasoned” Marine Corps combat leaders in 1941. Moreover, had it not been for the efforts of Colonel Earl Hancock “Pete” Ellis, author of a thesis written at the Navy War College concerning advanced naval bases (1910) and later, the author of Operation Plan 712: Advanced Base Force: Operations in Micronesia, there would have been no amphibious warfare doctrine in 1941, which was critical to the defense of American interests in the Pacific leading up to World War II.
On 7 December 1933, the Secretary of the Navy established the Fleet Marine Force (FMF). Its purpose was to modernize the concept of amphibious warfare — initially published and implemented as the Tentative Landing Operations Manual, 1935. This manual was a doctrinal publication setting forth the theory of landing force operations, organization, and practice. The Landing Operations Manual prescribed new combat organizations and spurred the development of state-of-the-art amphibious landing craft and ship-to-shore tractors. The document also addressed aerial and naval support during amphibious landings. To test these new ideas, the Secretary of the Navy directed a series of Fleet Landing Exercises (FLEX). FLEXs were conducted in the Caribbean, along the California coast, and in the Hawaiian Islands. All FLEX exercises were similar to, or mirror images of exercises undertaken by Colonel Ellis in 1914.
The Marine Corps continued this work throughout the 1930s by identifying strategic goals for the employment of FMF units, along with training objectives for all FMF-type units: infantry, artillery, aviation, and logistics. Oddly, during this period, Major General Commandant Ben H. Fuller decided that the Marine Corps did not need organic artillery. Fuller reasoned that since landing forces would operate within the range of naval gunfire, artillery units were an unnecessary expense.
General Fuller’s rationale was seriously flawed, however. The Navy could be depended upon to “land the landing force,” but the safety of combat ships in enemy waters prevented naval commanders from committing to the notion of “remaining on station” while the Marines conducted operations ashore. Accordingly, the Secretary of the Navy overruled Fuller, directing that FLEX exercises incorporate Marine Corps artillery (provided by the 10th Marines), which at the time fielded the 75-mm pack howitzer.
With its new emphasis on amphibious warfare, the Marine Corps readied itself for conducting frontal assaults against well-defended shore installations — with infantry battalions organized to conduct a sustained operation against a well-fortified enemy. When Germany invaded Poland in 1939, President Franklin D. Roosevelt announced a “limited national emergency.” Doing so permitted the Marine Corps to increase its recruiting to authorized wartime strength — including Advance Defense Battalions (ADB).
At first, ADBs operated as expeditionary coastal artillery units capable of occupying an undefended beach and establishing “all-around” sea-air defenses. The average strength of the ADB was 1,372 Marines; their armaments included eight 155-mm guns, 12 90-mm guns, 25 20-mm guns, and 35 50-caliber machine guns. The staffing demand for twenty (20) ADBs initially fractured the Marine Corps’ artillery community, but approaching Japan’s sneak attack on 7 December 1941, HQMC began organizing its first infantry divisions, including a T/O artillery regiment.
World War II
During World War II, the Marine Corps formed two amphibious corps, each supported by three infantry divisions and three air wings. In 1941, the capabilities of artillery organizations varied according to weapon types. For instance, the 10th Marines might have 75mm pack howitzers, while the 11th Marines might field 155-mm howitzers. But, by 1942, each artillery regiment had three 75-mm howitzer battalions and one 105-mm howitzer battalion. An additional 105-mm howitzer battalion was added to each regiment in 1943. By 1945, each artillery regiment hosted four 105-mm battalions.
The Marine Corps re-activated the 11th Marines on 1 March 1941 for service with the 1st Marine Division (1stMarDiv). The regiment served on Guadalcanal (1942), Cape Gloucester (1943), Peleliu (1944), and Okinawa (1945). At the end of World War II, the 11th Marines also served in China as part of the Allied occupation forces, returning to Camp Pendleton, California, in 1947.
HQMC re-activated the 10th Marines on 27 December 1942. Assigned to the 2ndMarDiv, the 10th Marines served on Tarawa, Saipan, Tinian, and Okinawa. During the Battle of Okinawa, the 10th Marines served as a reserve artillery force. After Japan’s surrender, the 10th Marines performed occupation duty in Nagasaki, Japan. The regiment returned to the United States in June 1946.
HQMC activated the 12th Marines on 1 September 1942 for service with the 3rdMarDiv, where it participated in combat operations at Bougainville, Guam, and Iwo Jima. The 12th Marines were redeployed to Camp Pendleton, California, and de-activated on 8 January 1946.
The 14th Marines reactivated on 1 June 1943 for service with the 4thMarDiv. The regiment served at Kwajalein, Saipan, Tinian, and Iwo Jima. Following the Battle of Iwo Jima, the 14th Marines returned to Hawaii, then to Camp Pendleton, where it disbanded on 20 November 1945.
HQMC activated the 13th Marines for service with the 5thMarDiv on 10 January 1944. Following operations on Iwo Jima, the regiment performed as an occupation force at Kyushu, Japan. The 13th Marines deactivated at Camp Pendleton, California, on 12 January 1946.
The 15th Marines was activated to serve with the 6thMarDiv on 23 October 1943. This regiment participated in the Battle of Okinawa and later as an occupation force in Tsingtao, China. The 15th Marines deactivated on 26 March 1946 while still deployed in China.
(Continued Next Week)
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- Buckner, D. N. A Brief History of the 10th Marines. Washington: US Marine Corps History Division, 1981
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- Emmet, R. A Brief History of the 11th Marines. Washington: Headquarters, U. S. Marine Corps, 1968
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- Shulimson, J., and C. M. Johnson. US Marines in Vietnam: The Landing and the Buildup, 1965. Washington: Headquarters, U.S. Marine Corps, 1978.
- Smith, C. R. A Brief History of the 12th Marines. Washington: Headquarters, U.S. Marine Corps, 1972.
- Strobridge, T. R. History of the 9th Marines. Quantico: Gray Research Center, 1961, 1967.
 The Advanced Base Force later evolved into the Fleet Marine Force (FMF).
 Embarking a Marine combat force aboard US Navy ships or conducting amphibious operations is not a simple task. The officers and men who plan such operations, and those who implement them, as among the most intelligent and insightful people wearing an American military uniform.
 In August 1942, the threat to the Navy’s amphibious ready group by Imperial Japanese naval forces prompted Vice Admiral Frank J. Fletcher, Commander, Task Force 61, to withdraw his force from Guadalcanal before the 1stMarDiv’s combat equipment and stores had been completely offloaded. Fletcher’s decision placed the Marines in a serious predicament ashore, but the Battle of Savo Island on 9 August proved that Fletcher’s decision was tactically sound.
 A howitzer is a rifled field gun that stands between a cannon and a mortar. Howitzers are organized as “batteries.” The 75-mm Howitzer (M-116) was designed in the 1920s to meet the need for a field weapon capable of movement across difficult terrain. In other words, the weapon could be “packed” into barely accessible areas and used to provide direct artillery support to infantry units.
 Such was the 1st Defense Battalion at Wake Island between 8-23 December 1941.