The U.S. Military in the
Interwar Years
Army duties just after the War
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Guarding Mexican border: 1919-20
Occupation forces in Germany: 1918-23
Missions into the Soviet Union: 1918-20
China garrison (Tientsin)
Coping with domestic disturbances: 191920
Demobilization
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3,250,000 men released by August 1919
By end of 1919, Army strength at:
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205,000 enlisted men
19,000 officers
all volunteers
National Defense Act of 1920
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Creates the Army of the United States,
composed of:
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professional Regular Army
National Guard units
“Organized Reserves”
The Regular Army and the 1920 Act
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Maximum size of 280,000.
Responsibilities:
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Provide troops for overseas garrisons, border
defense, expeditionary forces
Train army’s civilian components
Guard
 Reserves
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Other aspects of the 1920 Act
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Bolstered importance of ROTC.
Allocated responsibility for economic
mobilization/planning to the Assistant
Secretary of War
Division became basic Army unit.
War Plan Orange
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U.S. military considered Japan most likely
belligerent in years after WWI.
The Washington Conference of
1921-22
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Five Power Treaty - Limits on capital ship
construction:
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Total fleet tonnage ratio
Ship tonnage & gun size limit
10-year building “holiday”
Four Power Treaty
Nine Power Treaty
1930’s Developments
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London Conference of 1930:
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Japan walks out of 1935 London
Conference.
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Tonnage ratios for cruisers.
Building holiday for capital ships extended.
Renounces naval treaties in 1936.
U.S. naval construction legislation.
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Vinson-Trammell Act, 1934.
Naval Act of 1938.
Naval Advances
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Carriers
Submarines
Amphibious tactics
American Prophet of Air Power
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Billy Mitchell
Italian Prophet:
Guilio Douhet
1921 Navy Bombing Tests
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Ostfriesland sunk in
Chesapeake Bay
Organization of U.S. Military
Aviation
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1920: Air Service becomes a branch of the
Army.
1926: Air Service becomes the Air Corps.
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Assistant Secretary for War (Air) created
Air officers added to General Staff
Force expansion
“Father” of Naval Aviation
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William A. Moffett
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Becomes chief of
Navy’s new Bureau of
Aeronautics in 1921.
Pre-War Focus of Army Air Corps:
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Bombing
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particularly industrial
targets.
eschewed bombing
civilians
What about the rest of the Army?
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During 1920’s & most of 1930’s:
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undermanned
scattered
minimal resources for new weapons
some planning for economic mobilization
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Industrial Mobilization Plan of 1930
Douglas MacArthur,
Army Chief of Staff, 1930-35
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Reorganization:
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Sought to create a force
that could deploy quickly
in case of emergency.
Created four Army HQ’s.
Pushed mechanization of
Regular divisions.
Included National Guard
units.
Some weapon improvements
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M-1 Garand
semiautomatic rifle
105mm howitzer
60 & 81mm mortars
Tanks?