World War II: Interwar Period & The Road to War

Tactical and Technological Innovations of World War I

Communications Equipment and Personal Gear:
- Wireless Radio: Deployed in field operations to enable long-distance operational signaling across active fronts.
- Infantry Helmets: Distinctive headgear adopted by combatants included the German M 1916 helmet (steel helmet with prominent lugs) and the British M1 helmet (shallow bowl design).
Aviation Advancements:
- Fighter Aircraft: The SPAD S.XIII (PU.145) biplane served as a primary pursuit fighter aircraft.
- Strategic Bombing: The German Gotha bombers introduced long-range strategic aerial bombardment against enemy industrial and urban targets.
Automatic Weapons and Heavy Artillery:
- Vickers Gun: Heavy water-cooled machine gun providing continuous defensive suppressive fire.
- Artillery Tactics: Heavy artillery batteries (such as French heavy artillery) were used to execute pre-assault bombardments to "soften up" enemy positions prior to infantry advances.
Architecture of Trench Warfare:

*   **Front Line Trench (A)**: The forward-most combat trench directly facing the enemy line.
*   **Support Trench (B)**: Located behind the front line to hold tactical reserves and immediate combat supplies.
*   **Reserve Trench (C)**: Positioned further to the rear to shelter troops staged for counterattacks or battle rotations.
*   **Communication Trenches**: Interconnected deep passageways linking the front line, support, and reserve trenches to allow safe movement of troops and material under fire.
*   **Dugouts**: Fortified underground shelters excavated into trench walls to protect command posts and personnel during heavy bombardments.
*   **Barbed Wire Entanglements**: Extensive defensive obstacle belts placed in front of the front line trenches to break up enemy infantry attacks.
*   **Saps**: Shallower trenches constructed extending forward into "No Man's Land" to provide direct, covered access to forward machine-gun nests, grenade-throwing posts, and observation posts.
*   **No Man's Land**: The lethal open ground separating opposing trench networks, varying in width from 25 yards to a full mile.

Armored Warfare and Special Forces Tactics:
- Tanks: First operational deployment occurred on September 15, 1916, when the British military introduced heavy tanks to breach barbed wire and cross trench systems.
- Stosstruppen (Stormtroopers): Specialized German infiltration infantry trained in decentralized, shock-assault tactics to bypass heavily fortified strongpoints.

World War I Casualty Statistics and Interwar Border Re-alignments

Comparative Human Casualties:
- Allies and Associated Powers (Approximate Total Casualties):
  - Russia: 6,700,000
  - France: 5,920,650
  - Great Britain: 3,050,000
  - Belgium: 552,000
  - USA: 262,725
- Central Powers (Approximate Total Casualties):
  - Germany: 5,768,000
  - Austria-Hungary: 5,377,283
  - Ottoman Empire: 650,000
  - Bulgaria: 90,000 (dead)
Interwar Territorial Losses (1918–1939):

Map of Interwar European Territorial Losses

*   **Germany**: Lost Alsace-Lorraine to France, Eupen-Malmedy to Belgium, Northern Schleswig to Denmark, Posen/West Prussia/Polish Corridor to Poland, and Memel to Lithuania, while the Saar Basin was placed under League of Nations administration and the Rhineland was designated a demilitarized zone.
*   **Austria-Hungary**: Completely dissolved into independent successor states (Austria, Hungary, Czechoslovakia, Yugoslavia) while yielding territory to Poland, Romania, and Italy.
*   **Russia**: Relinquished control over Finland, Estonia, Latvia, Lithuania, Poland, and Bessarabia following war and revolution.
*   **Bulgaria**: Ceded border territories to Greece and Yugoslavia.

Interwar Diplomacy: The Years of Optimism (1919–1928)

The League of Nations (Société des Nations): Established as a international collective security body aimed at resolving sovereign disputes through arbitration.
1921–1922 Washington Naval Conference:
- Strategic Objectives: Responded to an accelerating international naval arms race and rising strategic threats posed by Japanese expansionism in the Far East, targeting capital fleet reductions for Britain and Japan.
- Conference Participants:
  - Naval Arms Reduction: United States, Great Britain, Japan, Italy, and France.
  - Far East Security: Belgium, China, Portugal, and the Netherlands.
- The Five Power Treaty: Established strict capital ship total tonnage ratios among the major naval powers set at $5 : 5 : 3 : 1.75 : 1.75$ (United States : Great Britain : Japan : France : Italy).
- Fleet Provisions: Mandated a complete moratorium on constructing new capital ships and required scrapping older battleships, while permitting signatories to convert existing capital warship hulls into aircraft carriers.

*   **Pacific Restrictions**: Capped the construction of new military fortifications across designated Pacific island territories.

1930 London Naval Treaty:
- Extended naval limitations by establishing heavy cruiser tonnage ratios at $18 : 15 : 12$ (United States : Great Britain : Japan).
- Capped total tonnage for light cruisers.
- Restricted maximum submarine gun calibers.
- Mandated prize rules requiring attack submarines to surface and allow merchant crews time to safely board lifeboats before sinking vessels.
1925 Locarno Treaties:

*   **Signatories**: Belgium, France, Germany, Great Britain, and Italy.
*   **Terms**: Defined the territorial borders of Western Europe as permanent and inviolable, confirmed the demilitarized status of the Rhineland, and established mutual military assistance guarantees in the event of unprovoked aggression.
*   **Key Diplomatic Architects**: Gustav Stresemann (Germany), Austen Chamberlain (Great Britain), and Aristide Briand (France).

1928 Kellogg-Briand Pact:
- International agreement negotiated and signed by nations including Germany, France, Great Britain, Belgium, and the United States.
- Pledged all signatory states to formally renounce war as an instrument of national policy and to settle all international disputes solely through peaceful diplomatic means.

Rise of Totalitarian Dictatorships

Fascist Italy:
- Benito Mussolini established a Fascist dictatorship following the armed "March on Rome" in October 1922.
National Socialism in Germany:
- 1923 Beer Hall Putsch: Failed armed coup in Munich led by Adolf Hitler alongside General Erich Ludendorff. Defendants included Pernet, Weber, Frick, Kriebel, Ludendorff, Hitler, Brückner, Röhm, and Wagner.

*   **Ideological Blueprint**: Published in Hitler's political manifesto *Mein Kampf* (issued by Eher-Verlag).
*   **Chancellorship**: Adolf Hitler was legally appointed Reich Chancellor on January 30, 1933.

Consolidation of Nazi State Power (1934):
- June 30, 1934 ("Night of the Long Knives"): Blood purge directed by Hitler and the SS to liquidate the leadership of the paramilitary SA Brownshirts (headed by Ernst Röhm) to secure political dominance and win the support of the professional regular army (Reichswehr, under Hans von Seeckt).
- Personal Oath: German military officers and enlisted men were required to swear a binding oath of unconditional personal obedience to Adolf Hitler.
- July 25, 1934 (Austrian Crisis): Austrian Nazis launched an attempted Putsch and assassinated Austrian Dictator Engelbert Dollfuss. Benito Mussolini responded by deploying Italian troops directly to the Italo-Austrian border, forcing Hitler to publicly disavow the coup ("hands off Austria").
Stalin's Red Army Purges (1937–1939):
- Underlying Causes: Driven by Joseph Stalin's intense suspicion of professional military commanders, prioritizing "loyalty, orthodoxy, and intellectual subservience" over military competence.
- Extent of Military Liquidation:
  - 30,000 out of 75,000 to 80,000 Red Army officers were purged.
  - 10,000 officers were discharged.
  - 3 out of 5 Marshals of the Soviet Union were purged (including Mikhail Tukhachevsky; Kliment Voroshilov assisted Stalin).
  - 11 out of 11 Deputy Defense Commissars were eliminated.
  - All military district commanders were removed.
  - The operational heads of both the Air Force and Navy, alongside their chiefs of staff, were purged.
  - 14 out of 16 Army Commanders were purged.
  - 60 out of 67 Corps Commanders were purged.
  - 136 out of 199 Division Commanders were purged.
  - 221 out of 397 Brigade Commanders were purged.
  - Approximately half of all Regimental Commanders were purged.
- Operational Impacts: Destruction of officer corps continuity resulted in severe degradation of unit training and material maintenance, leading directly to the institutional abandonment of advanced Soviet operational doctrines like "Deep Battle" and