1915 CE

A year dominated by the escalation of World War I on multiple fronts, the beginning of the Armenian Genocide, and Albert Einstein's completion of his general theory of relativity.

Geopolitics & Diplomacy

Italy signed the secret Treaty of London on April 26, promising territorial gains in exchange for joining the Allied Powers against Austria-Hungary and Germany.
Italy declared war on Austria-Hungary on May 23, opening a new front along the Isonzo River and expanding the scope of the European conflict.
Japan presented the Twenty-One Demands to China on January 18, seeking extensive economic and political concessions that would establish Japanese dominance over Chinese affairs.
China accepted a modified version of Japan's Twenty-One Demands on May 25, ceding significant economic privileges in Manchuria and Shandong while resisting the most extreme provisions.
Bulgaria entered World War I on the side of the Central Powers in October, joining the attack on Serbia and dramatically altering the balance of power in the Balkans.
The sinking of the RMS Lusitania on May 7 by a German U-boat, killing 1,198 passengers including 128 Americans, strained German-American diplomatic relations.
U.S. Secretary of State William Jennings Bryan resigned on June 9 over disagreements with President Wilson's firm diplomatic stance toward Germany following the Lusitania sinking.
Britain and France established a naval blockade of Germany, restricting imports of food and raw materials and contributing to severe civilian hardship in the Central Powers.
Greece remained officially neutral despite Allied pressure, as King Constantine I resisted Prime Minister Venizelos's push to join the Entente.
Persia declared neutrality in the war, but its territory became a battleground as Ottoman, Russian, and British forces operated within its borders.

Conflict & Security

The Allied campaign at Gallipoli began on April 25 with landings at Cape Helles and Anzac Cove, marking a major attempt to knock the Ottoman Empire out of the war.
The Second Battle of Ypres began on April 22, during which Germany used chlorine gas on a large scale for the first time on the Western Front, killing thousands of Allied soldiers.
The Armenian Genocide began in April when Ottoman authorities arrested and deported Armenian intellectuals from Constantinople, initiating a systematic campaign that would kill an estimated 1.5 million Armenians.
Serbia was invaded by combined Austro-Hungarian, German, and Bulgarian forces in October, forcing the Serbian army into a catastrophic retreat through Albania.
The Battle of Loos, the largest British offensive of 1915, began on September 25 on the Western Front, resulting in heavy casualties for limited territorial gains.
Germany launched unrestricted submarine warfare in February, declaring the waters around the British Isles a war zone and targeting merchant shipping.
Russian forces suffered a devastating defeat at the Battle of Gorlice-Tarnow in May, as a combined German-Austrian offensive drove them out of Galicia and Poland.
The Gallipoli campaign stalled as Turkish forces under Mustafa Kemal held the heights at Chunuk Bair and repulsed repeated Allied attempts to advance inland.
Italy launched the first four Battles of the Isonzo between June and December, suffering heavy casualties in frontal assaults against well-defended Austrian positions.
South African and British forces completed the conquest of German South-West Africa in July, securing one of Germany's colonial territories in Africa.

Economy & Finance

Britain introduced its first wartime budget under Chancellor Reginald McKenna in September, raising income tax and imposing new duties on imported luxury goods.
The British government took control of the munitions industry through the Ministry of Munitions, established in June under David Lloyd George to address a severe shell shortage.
Germany's economy began to suffer under the Allied naval blockade, with shortages of food and raw materials affecting both military and civilian sectors.
The United States experienced an economic boom as European demand for American manufactured goods, food, and raw materials surged.
American banks extended large loans to the Allied Powers, with J.P. Morgan & Co. organizing a $500 million Anglo-French bond issue in October.
The cotton trade was severely disrupted by the war, devastating the economies of the American South and colonial producers in Egypt and India.
France mobilized its economy for total war, requisitioning factories and redirecting industrial production toward military needs.
Inflation began to rise in most belligerent nations as governments printed money to finance the enormous costs of the war.
Canada's wartime economy expanded rapidly as orders for munitions, food, and military supplies flowed from Britain.
The Trans-Siberian Railway became a crucial supply line for Russia, transporting war materials from Vladivostok to the Eastern Front.

Technology & Infrastructure

The first transcontinental telephone call was made on January 25, when Alexander Graham Bell in New York spoke with Thomas Watson in San Francisco.
Germany deployed poison gas at the Second Battle of Ypres in April, introducing chemical warfare as a new and terrifying dimension of modern combat.
The Fokker Eindecker monoplane entered service with the German Air Force, using a synchronized machine gun to fire through the propeller arc and establishing fighter aviation.
Tanks were under development in Britain as the Landships Committee, formed in February, began designing armored vehicles to cross trench lines.
The first all-metal aircraft, the Junkers J 1, made its maiden flight in Germany on December 12, pioneering a shift from wood-and-fabric construction in aviation.
Pyrex heat-resistant glassware was introduced by Corning Glass Works, originally developed for railroad signal lanterns and later adapted for laboratory and kitchen use.
Depth charges were first deployed by the Royal Navy to counter the growing threat of German submarines.
NACA, the National Advisory Committee for Aeronautics, was established by the U.S. Congress on March 3 to promote aeronautical research.
Radio communication advanced rapidly under wartime demand, with military forces on all sides using wireless telegraphy for battlefield coordination.
The Rocky Mountain locust-proof grain elevator system expanded across the Canadian prairies to handle the increased wartime demand for wheat exports.

Science & Discovery

Albert Einstein presented his general theory of relativity to the Prussian Academy of Sciences in November, fundamentally redefining the understanding of gravity, space, and time.
Alfred Wegener published the expanded edition of The Origin of Continents and Oceans, proposing the theory of continental drift despite widespread scientific skepticism.
William Henry Bragg and his son William Lawrence Bragg were awarded the Nobel Prize in Physics for their pioneering analysis of crystal structures using X-ray diffraction.
Richard Willstatter received the Nobel Prize in Chemistry for his research on plant pigments, particularly chlorophyll.
Einstein published his field equations of general relativity in a series of papers presented to the Prussian Academy between November 4 and November 25.
British physicist Henry Moseley, who established the concept of atomic number through X-ray spectroscopy, was killed at Gallipoli on August 10 at age 27.
Physicist Arnold Sommerfeld extended the Bohr model of the atom by introducing elliptical orbits and additional quantum numbers.
Frederick Twort published his discovery of bacteriophages, viruses that infect bacteria, opening a new field of microbiology.
Paul Langevin began developing early sonar technology using piezoelectric transducers, driven by the need to detect German submarines.
Karl Schwarzschild, serving on the Eastern Front, derived the first exact solution to Einstein's field equations, describing the geometry of space around a spherical mass.

Health & Medicine

Typhus epidemics ravaged Serbia during the winter and spring, killing an estimated 150,000 people, including a significant portion of the country's medical personnel.
Wounded soldiers on all fronts suffered from infected injuries, driving research into antiseptics and wound treatment under battlefield conditions.
Henry Dakin and Alexis Carrel developed the Carrel-Dakin method of wound irrigation using a sodium hypochlorite solution, significantly reducing infection rates in battlefield wounds.
Blood transfusion techniques advanced during the war, with Richard Lewisohn demonstrating that sodium citrate could prevent blood from clotting, making stored blood transfusion practical.
Prosthetic limb technology advanced as the war produced unprecedented numbers of amputees, spurring innovation in artificial limb design.
Shell shock was increasingly recognized as a medical condition, though understanding of its psychological causes remained limited and treatment was often inadequate.
The British Medical Research Committee, predecessor of the Medical Research Council, funded research on trench fever, a debilitating louse-borne illness affecting soldiers.
Chlorine gas exposure at Ypres caused thousands of casualties with lung damage, and medical responses to chemical weapons injuries were rapidly developed.
The Rockefeller Foundation expanded its international public health programs, funding campaigns against hookworm and yellow fever in the Americas and Asia.
Dental surgery advanced in military hospitals as maxillofacial reconstruction techniques were developed to treat soldiers with severe jaw and facial injuries.

Climate & Environment

Atmospheric carbon dioxide concentration was approximately 301 parts per million, as later determined through ice core analysis and early direct measurements.
The Galveston hurricane struck Texas on August 17, causing significant damage to the city that had been rebuilt after the devastating 1900 hurricane.
An earthquake struck Avezzano, Italy, on January 13, killing over 30,000 people and destroying much of the town in the Abruzzi region.
Wartime demand for timber accelerated deforestation across Europe, as armies consumed vast quantities of wood for trench construction, fuel, and infrastructure.
The landscape of northern France and Belgium was devastated by trench warfare, artillery bombardment, and chemical weapons, rendering vast areas of farmland uninhabitable.
Severe flooding struck Guangdong Province in China, displacing hundreds of thousands of people and destroying crops and infrastructure.
Wildlife populations declined in European war zones as habitat destruction and disruption from combat affected animal populations across the Western and Eastern Fronts.
Agricultural output fell in France and Belgium as fighting destroyed farmland and millions of men were conscripted away from food production.
The U.S. National Park Service organic act was in preparation as conservation advocates including Stephen Mather lobbied for a dedicated federal agency to manage national parks.
Overexploitation of fisheries in the North Sea declined sharply as naval warfare and mines made commercial fishing extremely dangerous.

Culture & Society

D.W. Griffith's film The Birth of a Nation premiered on February 8, becoming a landmark in cinema for its technical innovations while provoking outrage for its racist portrayal of Reconstruction.
The Women's Institute movement was founded in Britain in September, beginning as a rural women's organization that would grow into a major civic institution.
Franz Kafka published The Metamorphosis, a novella about a man who transforms into an insect, which became one of the defining works of modernist literature.
The Ku Klux Klan was revived at Stone Mountain, Georgia, on November 25, inspired by The Birth of a Nation and anti-immigrant sentiment.
John Buchan published The Thirty-Nine Steps, an espionage thriller that became a classic of the genre and was later adapted by Alfred Hitchcock.
Poet Rupert Brooke died of sepsis on April 23 while en route to Gallipoli, and his war sonnets became emblematic of early idealistic attitudes toward the conflict.
Motorized taxicab services continued expanding in American cities, with growing fleets replacing horse-drawn carriages and transforming urban transportation.
The International Congress of Women met at The Hague in April, with over 1,100 delegates from both belligerent and neutral nations calling for a negotiated end to the war.
Booker T. Washington, the prominent African American educator and founder of the Tuskegee Institute, died on November 14 at age 59.
The world population was approximately 1.88 billion.