Directory

1920 CE

A year in which the League of Nations held its first meeting, American women won the right to vote, Prohibition began in the United States, and the postwar world struggled to rebuild amid political upheaval.

Geopolitics & Diplomacy

  • The League of Nations held its first council meeting on January 16 in Paris, establishing the first permanent international organization dedicated to maintaining world peace.
  • The United States Senate voted against ratifying the Treaty of Versailles on March 19, keeping the country out of the League of Nations despite President Wilson's efforts.
  • The Treaty of Trianon was signed on June 4, dismembering the Kingdom of Hungary and reducing its territory by approximately two-thirds as part of the post-World War I settlement.
  • The Treaty of Sèvres was signed on August 10, partitioning the Ottoman Empire and granting territorial concessions to Greece, Italy, and France.
  • The Free City of Danzig was established on November 15 under League of Nations protection, creating a semi-autonomous city-state on the Baltic coast.
  • The Soviet-Polish War saw the Red Army advance toward Warsaw in the summer, threatening to spread Bolshevism into Central Europe.
  • The Conference of San Remo in April assigned League of Nations mandates for Palestine, Mesopotamia, and Syria to Britain and France.
  • The Åland Islands dispute between Sweden and Finland was referred to the League of Nations, marking one of the organization's first diplomatic tests.
  • Mandatory Palestine was established under British administration following the San Remo Conference, setting the stage for decades of conflict in the region.
  • Admiral Miklós Horthy became regent of Hungary on March 1, establishing an authoritarian conservative regime after the collapse of the short-lived Hungarian Soviet Republic.

Conflict & Security

  • The Polish-Soviet War reached its climax at the Battle of Warsaw in August, where Polish forces under Józef Piłsudski repelled the Red Army in what was called the Miracle on the Vistula.
  • The Russian Civil War continued as the Red Army fought the remnants of the White movement, with General Wrangel's forces holding out in Crimea until November.
  • The Greco-Turkish War intensified as Greek forces advanced into Anatolia following the Treaty of Sèvres, occupying Smyrna and pushing eastward.
  • The Irish War of Independence escalated with ambushes and reprisals, as the IRA carried out guerrilla attacks against British forces throughout Ireland.
  • Bloody Sunday occurred on November 21 in Dublin, when IRA operatives killed fourteen British intelligence agents and the Black and Tans retaliated by firing into a crowd at Croke Park, killing fourteen civilians.
  • The Red Army defeated the last major White Russian forces under General Wrangel in Crimea in November, effectively ending the Russian Civil War in European Russia.
  • The Kapp Putsch attempted to overthrow the Weimar Republic in March, but collapsed after four days when a general strike paralyzed Berlin.
  • Arab-Jewish tensions in Palestine erupted in the Nebi Musa riots in April, with violent clashes in Jerusalem leaving several dead and many wounded.
  • The Kingdom of Iraq experienced a major revolt against British rule beginning in June, with widespread tribal uprisings that required months of military operations to suppress.
  • Violence continued in the aftermath of the Russian Civil War as various factions fought across Central Asia and the Caucasus.

Economy & Finance

  • The United States entered a sharp postwar recession in January, as wartime industries contracted and demobilized soldiers flooded the labor market.
  • Prohibition took effect in the United States on January 17 under the Eighteenth Amendment, banning the manufacture, sale, and transport of alcoholic beverages.
  • German war reparations under the Treaty of Versailles placed enormous financial pressure on the Weimar Republic, contributing to economic instability.
  • The price of commodities collapsed in the postwar economic downturn, devastating farmers in the United States and other agricultural exporters.
  • Hyperinflation began to take hold in Austria and Hungary as the successor states of the former Habsburg Empire struggled with enormous war debts.
  • Britain faced rising unemployment and industrial unrest as the postwar economic boom gave way to a severe recession.
  • Japan experienced a financial panic in March when stock prices collapsed on the Tokyo exchange, ending the country's wartime economic boom.
  • The first meeting of the International Chamber of Commerce took place in Paris in June, aiming to promote international trade and investment.
  • The U.S. economy saw rapid deflation as wholesale prices fell sharply from their wartime peaks, causing widespread business failures.
  • Coal miners in Britain staged widespread strikes in October, protesting wage cuts and poor working conditions in the depressed postwar economy.

Technology & Infrastructure

  • Radio station KDKA in Pittsburgh conducted what is widely considered the first commercially licensed radio broadcast on November 2, reporting the results of the Harding-Cox presidential election.
  • The first commercial radio broadcast in the United Kingdom was made by the Marconi Company from its Chelmsford factory in February, featuring a concert by Dame Nellie Melba.
  • The Panama Canal was officially opened to unrestricted traffic, having begun limited operations in 1914, and saw growing international shipping through its locks.
  • The first automatic telephone exchange in Britain was installed at Fleetwood, Lancashire, advancing the automation of telecommunications.
  • Automobile registrations in the United States surpassed 8 million, reflecting the rapid expansion of car ownership that was transforming American transportation and daily life.
  • Tommy gun prototypes were developed by John T. Thompson's Auto-Ordnance Corporation, with the Thompson submachine gun entering commercial production.
  • The first regular airmail service between London and Paris was established, marking the beginning of routine international air postal service in Europe.
  • Construction of the Holland Tunnel connecting Manhattan and New Jersey was authorized by the New York and New Jersey legislatures.
  • Albert Michelson measured the diameter of the star Betelgeuse using an interferometer mounted on the 100-inch telescope at Mount Wilson Observatory, marking the first measurement of a star's angular size.
  • The first commercially successful electric food mixer was introduced by the Hobart Manufacturing Company under the KitchenAid brand.

Science & Discovery

  • Arthur Eddington published Space, Time and Gravitation, popularizing Einstein's general theory of relativity for a broad scientific audience.
  • Ernest Rutherford proposed the existence of the neutron in his Bakerian Lecture, hypothesizing that a neutral particle existed in the atomic nucleus.
  • Otto Stern and Walter Gerlach began experiments on space quantization of atomic angular momentum, which would produce landmark results by 1922.
  • Arthur Eddington published his influential work on stellar structure and the internal constitution of stars, advancing theoretical astrophysics.
  • Andrew Douglass refined the technique of dendrochronology, using tree ring patterns to establish precise calendars for dating archaeological sites in the American Southwest.
  • Astronomers at the Harvard College Observatory continued cataloging stellar spectra, expanding the Henry Draper Catalogue that classified hundreds of thousands of stars.
  • Norwegian meteorologists Vilhelm and Jacob Bjerknes advanced the polar front theory, establishing the modern framework for understanding mid-latitude weather systems.
  • John B. Watson and Rosalie Rayner conducted the Little Albert experiment, demonstrating classical conditioning of fear in a human infant and advancing behaviorist psychology.
  • Frederick Soddy published his work on isotopes, demonstrating that elements could exist in forms with different atomic masses, for which he would receive the Nobel Prize the following year.
  • Meghnad Saha published his ionization equation, providing a theoretical basis for classifying stellar spectra by relating a star's spectral features to its temperature and pressure.

Health & Medicine

  • The global influenza pandemic that had killed an estimated 50 million people since 1918 finally subsided, though sporadic outbreaks continued in several countries.
  • Insulin had not yet been discovered, and diabetes remained a fatal diagnosis managed only through starvation diets developed by Frederick Allen and Elliott Joslin.
  • The first clinical trials of the BCG tuberculosis vaccine were conducted in France by Albert Calmette and Camille Guérin, beginning with animal testing and limited human application.
  • August Krogh received the Nobel Prize in Physiology or Medicine for his discovery of the capillary motor regulating mechanism, explaining how blood flow is controlled in capillaries.
  • Typhus epidemics ravaged Eastern Europe and Russia as the aftermath of war, famine, and displacement created conditions favorable to the disease.
  • Public health campaigns against hookworm expanded in the American South, supported by the Rockefeller Sanitary Commission's efforts since 1910.
  • Shell shock, later recognized as combat-related psychological trauma, affected tens of thousands of World War I veterans, though treatment remained rudimentary.
  • The Red Cross expanded its peacetime mission, establishing programs for disaster relief, public health nursing, and disease prevention in multiple countries.
  • Pellagra remained a major public health problem in the American South, with thousands of cases linked to nutritional deficiency among impoverished populations.
  • Dental health research advanced as scientists studied the connection between fluoride in drinking water and reduced rates of tooth decay.

Climate & Environment

  • Atmospheric carbon dioxide concentration was approximately 303 parts per million, as estimated from ice core records and early chemical measurements.
  • The Gansu earthquake struck the Haiyuan region of China on December 16, measuring approximately 8.5 on the Richter scale and killing an estimated 200,000 people.
  • Severe drought struck parts of northern China, contributing to famine conditions that affected millions of people in the region.
  • The U.S. National Park Service managed eighteen national parks, with visitation growing as automobile ownership expanded across the country.
  • Deforestation continued at a rapid pace in the northeastern United States as old-growth forests were cleared for lumber and agriculture.
  • The Mississippi River experienced significant flooding in spring, affecting communities along its lower reaches.
  • The Norwegian government established Rondane as one of the country's early nature protection areas, preserving mountain wilderness in central Norway.
  • Overfishing of Atlantic cod and herring stocks raised concerns among European fisheries scientists about the sustainability of commercial fishing.
  • Soil erosion on the American Great Plains worsened as wartime wheat cultivation had stripped native grasslands from millions of acres.
  • A major tropical cyclone struck the Gulf Coast of the United States in September, causing significant damage and loss of life along the coastline.

Culture & Society

  • The Nineteenth Amendment to the United States Constitution was ratified on August 18, guaranteeing American women the right to vote.
  • The first commercial radio broadcasts helped launch the age of mass media, transforming how news and entertainment reached the public.
  • F. Scott Fitzgerald published This Side of Paradise, his debut novel capturing the disillusionment and ambitions of the postwar American generation.
  • The Harlem Renaissance gained momentum as African American artists, writers, and musicians began reshaping American culture from their base in New York City.
  • The 1920 Summer Olympics were held in Antwerp, Belgium, the first Games after World War I, featuring athletes from 29 nations.
  • Agatha Christie published her first detective novel, The Mysterious Affair at Styles, introducing the character Hercule Poirot.
  • The American Professional Football Association, later renamed the National Football League, was founded in Canton, Ohio, on September 17.
  • Prohibition gave rise to speakeasies and bootlegging operations across the United States, reshaping American social life and organized crime.
  • Edith Wharton published The Age of Innocence, winning the Pulitzer Prize for Fiction the following year.
  • The world population was approximately 1.86 billion.