The Interwar Years: Exhaustive Study Guide

Chronology of the Interwar Period

• $1919$: Treaty of Versailles; North Russian intervention ends.
• $1920$: Marines occupy Haiti; National Defense Act of $1920$.
• $1921$: Siberian intervention ends; General Billy Mitchell sinks the Ostfriesland with Army bombers; Washington Naval Conference begins.
• $1922$: Occupation of Germany ends.
• $1923$: Court-Martial of Colonel Billy Mitchell.
• $1926$: Army Air Corps established; Marines intervene in Nicaragua.
• $1928$: Bonus Army marches on Washington, D.C.; Kellogg-Briand Pact signed.
• $1929$: New York Stock Exchange crashes.
• $1930$: London Naval Conference.
• $1931$: Japan invades Manchuria.
• $1933$: Hitler elected Chancellor of Germany.
• $1935$: Italy invades Ethiopia; Hitler renounces the Treaty of Versailles.
• $1937$: Japan invades China.
• $1938$: Naval Act of $1938$; RAINBOW plans developed.
• $1939$: Germany seizes Czechoslovakia; Germany invades Poland.

Postwar Transition and Domestic Responsibilities

• Introduction to Postwar Strategy: The Great War challenged American military traditions. Despite the Senate’s rejection of Woodrow Wilson’s League of Nations, the U.S. moved toward a policy of unilateralism with multilateral coordination for security concerns. The U.S. led disarmament efforts while increasing its own military potential using the Atlantic and Pacific oceans as security moats.
• Demobilization Challenges: After November $1918$, the U.S. had to discharge servicemen at a rate that balanced bringing them home quickly without harming the economy or neglecting occupation duties. Troop transport was a significant limiting factor.
• Industrial Surplus: Because mobilization had just reached peak levels when the war ended, the War Department maintained huge surpluses of $1918$-era equipment, which inadvertently stalled the procurement of modern technology through the $1920s$ and $1930s$.
• The Bonus Army ($1932$): Veterans seeking early payment of bonuses for their service during the Great War established a shantytown in Washington, D.C. President Hoover ordered General Douglas MacArthur to disperse the group. MacArthur led $600$ cavalry and infantry including Majors Dwight Eisenhower and George Patton. The dispersal resulted in the burning of the shantytown and controversy for MacArthur and the Army.
• The Civilian Conservation Corps (CCC): Established in $1933$ as a New Deal program, the Army mobilized over $300,000$ men at more than $1,000$ camps. While primarily an economic relief program for the Great Depression, it provided regular and reserve officers with significant command experience.

The National Defense Act of 1920 and Army Structure

• Army Organization: The National Defense Act of $1920$ scrapped the “expansible army” concept in favor of a modern, industrialized organization. It created the "Army of the United States," consisting of three parts:
  1. Regular Army: Professional soldiers.
  2. National Guard: Civilian-based state units.
  3. Civilian Reserves: Both officers and enlisted men.
• Authorized Strength: The act authorized over $17,000$ officers and $280,000$ enlisted personnel, though actual numbers remained lower due to a lack of threats and the Great Depression.
• Staff System (General Staff System): Pershing, as Chief of Staff in $1921$, organized the staff into four divisions:
  • G-1: Personnel.
  • G-2: Intelligence.
  • G-3: Training and Operations.
  • G-4: Logistics and Supply.
• Force Distribution: The Army was spread across nine commands (corps), with one regular, two National Guard, and three reserve divisions each. Military departments were also maintained in Panama, Hawaii, and the Philippines.
• Training and Education:
  • National Guard: Trained by regular officers $48$ times a year at armories and for $2$ weeks in the field.
  • Reserve Officer Training Corps (ROTC): By $1928$, over $325$ schools commissioned $6,000$ second lieutenants annually.
  • Citizens’ Military Training Camp (CMTC): A four-year summer program that qualified participants for reserve commissions, with over $30,000$ participants.
  • Advanced Schools: Includes the Command and General Staff College, the Army War College, and the Army Industrial College, focusing on producing competent commanders rather than theoretical study.

Professional Stagnation in Armor and Advancements in Airpower

• Armor Neglect: Army strategists viewed tanks only as infantry support. The Tank Corps was absorbed by the infantry. By World War II, the U.S. had only four mechanized units and one experimental tank brigade.
• Contrast with Europe: Great Britain gave armor independent roles. Germany’s Heinz Guderian pioneered "shock and awe" tactics with large, fast armor units.
• Airpower Theorists: Sir Hugh Trenchard (UK), Guilio Douhet (Italy), and Billy Mitchell (US).
  • Douhet’s Theory: Strategic bombing of civilian populations and industry could force government surrender, making wars shorter.
  • Conservative Doctrine: The Army and Navy argued aircraft were for artillery support, pursuit, and observation, not independent strategic success.
• The Ostfriesland Test ($1921$): Mitchell used Army bombers to sink the unmanned German battleship Ostfriesland off the Virginia Capes. He dropped over sixty $2,000$-pound bombs, scoring $16$ hits. Mitchell claimed victory over the battleship; the Navy claimed the test was invalid due to the lack of movement, antiaircraft fire, and the controlled environment.
• Mitchell’s Court-Martial ($1925$): Following crashes like the airship Shenandoah (where $14$ died), Mitchell accused the War and Navy Departments of “criminal negligence.” He was court-martialed for insubordination, demoted to colonel, and eventually resigned.
• Army Air Corps ($1926$): Created with an authorized $17,000$ men and $1,800$ aircraft. It established the Air Corps Tactical School at Maxwell Field, Alabama.

Naval Policy and International Limitation Treaties

• Washington Naval Conference ($1921-1922$): Aimed to prevent an arms race.
  • Five-Power Treaty: Established a ratio of $5:5:3:1.7:1.7$ for battleships and carriers between the U.S., UK, Japan, France, and Italy.
  • Four-Power Treaty: Signatories agreed to settle Far East possession disputes via conference.
  • Nine-Power Treaty: Signatories agreed to respect China’s Open Door policy.
• Naval Aviation Expansion: The Navy converted the Langley (collier) and the Lexington and Saratoga (cruisers) into carriers. Commanders like A.C. Read (first transatlantic flight, $1919$) and Richard E. Byrd (polar explorer) became icons.
• Treaty Collapse: Japan broke the treaties in the early $1930s$. The London Naval Conference ($1930$) failed due to an “escape clause” allowing nations to build if they felt threatened.
• Roosevelt’s Naval Build-up: FDR used the National Industrial Recovery Act ($1933$) and Vinson-Trammel Act ($1934$) to replace aging ships. By $1938$, the Naval Act authorized double the size of naval aviation.

Marine Corps Operations and Amphibious Doctrine

• Nicaragua Intervention ($1926-1933$): Marines protected American interests during a civil war between Liberals and Conservatives.
  • The Peace of Tipitapa: An agreement brokered by Henry Stimson.
  • Augusto Cesar Sandino: A Liberal band leader who refused the peace. The Marines engaged "Sandinistas" for five years. This conflict saw the first use of dive-bombing in military history.
• China Duty: The $3rd$ Brigade and $4th$ Marine Regiment guarded Shanghai and Tientsin in $1927$.
• Amphibious Warfare Theory: To avoid being just an “imperial constabulary,” the Marines studied the British failure at Gallipoli.
  • Tentative Manual for Landing Operations ($1934$): Outlined pre-landing bombardment, air support, and ship-to-shore communications.
  • Fleet Marine Force: Formed to coordinate with the Navy for beach assaults, though the Marine Corps numbered only $16,000$ in the mid-$1930s$.

Strategic War Planning and the RAINBOW Scenarios

• Industrial Mobilization Plan ($1930$): Sought to coordinate procurement but faced Congressional pushback for being too pro-industry and centralizing military control.
• Protective Mobilization Plan ($1937$): Organized industry and used the National Guard/Navy as the first line while the Army mobilized.
• Plan ORANGE: Joint Army-Navy plan for a Pacific war against Japan. It anticipated the loss of the Philippines and Guam followed by a slow retaking and a climactic Mahanian fleet action.
• RAINBOW Plans: Developed in $1938$ to handle two-ocean wars.
  • RAINBOW 1: Defense of the entire Western Hemisphere.
  • RAINBOW 2 & 3: Fighting Japan while allies fought Germany.
  • RAINBOW 4: Atlantic war fought without allies.
  • RAINBOW 5: Alliance with UK and France focusing on a “Defeat-Germany-First” strategy while holding a defensive line in the Pacific.

Verbatim: Colonel Billy Mitchell’s Statement to the Press, September 1925

Following the Shenandoah disaster, Mitchell stated:

— "I have been asked from all parts of the country to give my opinion about the reasons for the frightful aeronautical accidents and loss of life… These accidents are the direct result of the incompetency, criminal negligence and almost treasonable administration of the national defense by the Navy and War Departments."

— "All aviation policies, schemes and systems are dictated by the non-flying officers of the Army and Navy, who know practically nothing about it. The lives of airmen are being used merely as pawns in their hands."

— "As a patriotic American citizen, I can stand by no longer and see these disgusting performances by the Navy and War Departments… The bodies of my former companions of the air molder under the soil… many, yes, a great many, sent there directly by official stupidity."

Conclusion

• Kellogg-Briand Pact ($1928$): Aimed to outlaw war except for self-defense, signed by over $60$ countries. It proved ineffective against the rise of National Socialism and militaristic nationalism in Germany, Italy, and Japan.
• U.S. Preparedness: Despite economic crises and isolationist tendencies, the U.S. entered World War II with better mobilization plans and training than in $1917$. However, the military culture remained rigid, which would eventually require more flexibility for the conflicts ahead.