World War I causes

Five key causes of World War I

What caused World War I? The ready answer refers to the assassination of Archduke Franz Ferdinand. But there was more to it than that. This article, accompanied by a short explanatory video, outlines how mutual defense alliances, imperialism, militarism, and nationalism also had a heavy hand in the start of what some considered a "preventable war."

Illustrating the beginning and end of WWI through maps

In August of 1914, Germany invaded an ostensibly neutral Belgium, kick-starting World War I. The war became one of the deadliest conflicts in human history, decimating Europe and reshaping global politics for the next century. It also brought forward sweeping and terrifying new military technologies, a product of the Industrial Revolution. Explore 40 maps explaining the Great War in detail.

Who was impacted by the first world war, and how?

This interactive map from the National Archives in the UK details the global impact of World War I. Countries and territories from Aden to New Zealand were impacted by the Great War, which started in 1914 and lasted until 1918. By selecting various locations on the map, viewers can access articles and evidence on how the war's influence traveled far beyond the front lines.

Was WWI really the first world war?

Was World War I the first true international conflict? This article thoroughly explores the meaning of the term world war. It also suggests a few previous conflicts, some of which involved battles in the Americas as well as Europe, that might have been more accurately described as a "world wars."

The Concert of Europe's collapse contributed to World War I

The 19th-century great power system gradually unraveled due to rising nationalism, imperial rivalry, and shifting alliances—leading to its collapse in 1914 and the outbreak of the deadliest war the world had yet seen.

Everything you need to know about WWI

Summarizing World War I seems like an impossible task, but this article makes a great effort at providing a easily digested survey of the Great War. Read about WWI from the first shots fired by assassin Gavrilo Princip at the Archduke Franz Ferdinand and his wife Sophie, to the various campaigns waged by the war's participants, to the equipment provided to the various fighting forces.

The treaty that ended the First World War laid the groundwork for the Second

On June 28, 1919, the Treaty of Versailles officially ended World War I by demanding severe reparations, territorial losses, military restrictions, and the infamous “war guilt clause” against Germany. However, its harsh terms fostered deep resentment, economic instability, and political turmoil—ultimately becoming a catalyst for World War II.

The failures of the interwar period made the case for a new international system

After World War I, countries devalued their currencies, raised tariffs to block imports, and seized territory unchecked, with the international community unable to organize effectively to stop them. The result was a global depression and, eventually, another world war.

Exploring World War I technology on the battlefield

Industrialization brought massive changes to warfare during the Great War. Newly-invented killing machines begat novel defense mechanisms, which, in turn spurred the development of even deadlier technologies. Nearly every aspect of what we would consider modern warfare debuted on World War I battlefields. Starting with soldiers on horseback carrying lances and ending in poison gas, machine guns, and aerial battles, this gallery shows the first tools of modern warfare.

How the US entered WWI in 1917

Originally taking a position of neutrality during the course of World War I, the United States of America eventually relented. Entering the war in 1917, support for the British and French had risen and Americans were incensed by Germany's overtures to Mexico and U-boat attacks that sank ships and ended American lives. See how and why the US entered WWI in this article.

Explaining the final battle of World War I

The Meuse-Argonne Offensive was the last battle of the First World War. Beginning in September and ending November 11, 1918, the battle was a tumultuous event and the first time the American Army fought on the world's stage. America simultaneously achieved victory and discovered new methods to fight a war. This Apple History podcast provides the details.

What happened on WWI's Italian Front?

The battle in the Dolomites, or the White War, might have been the roughest, most arduous, and deadliest conflict during World War I. Italian and Austrian troops fought for control of the Dolomites mountain range over the course of three years, leading to the deaths of 700,000 Italian soldiers and 350,000 Austro-Hungarian troops. A grim account of a dirty little war high in the Dolomites.

Franklin D. Roosevelt's 1941 speech framed World War II as a global fight for universal rights

Eleven months before the attack on Pearl Harbor, President Roosevelt outlined four fundamental freedoms that, in his words, people "everywhere in the world" ought to enjoy—speech, worship, freedom from want, and freedom from fear.

Japan’s imperial expansion in Asia set the stage for war with the US

Between 1931 and 1941, Japan seized Manchuria, launched a full-scale war in China and occupied French Indochina, moves that intensified its demand for strategic resources and triggered escalating US-led embargoes—particularly the 1941 oil cutoff—which sharply raised the risk of war between the two countries.

How much did WWII cost?

Though it lasted fewer than four years, World War II was the most expensive war in United States history, according to this infographic. Read through it to see how much WWII cost and learn about the consequences of financing such an expensive conflict.

Why did the Ottoman Empire violently target Armenians during WWI?

In anticipation of threatened Allied landings at the strategically important Gallipoli peninsula, Ottoman authorities arrested 240 Armenian leaders in Constantinople on April 24, 1915, and deported them east. This roundup is commemorated today by Armenians as the beginning of the genocide, according to this article.

The “Phoney War” was an eight‑month build-up to war

From September 1939 to May 1940, following their war declaration on Germany, Britain and France entered a phase of military inaction—even as civil defence measures, naval blockades, and rationing intensified at home. Skirmishes were limited, but the decisive fighting didn't begin until Germany invaded Norway and France in April–May 1940, abruptly ending the uneasy stalemate.

The Cold War (1947-1991) prompted the birth of NATO and the Soviet Warsaw Pact

The geopolitical rivalry between the United States and Soviet Union was considered “cold" because the two countries never directly engaged in military combat during the time period. This page from the Kennedy Presidential Library outlines the causes and major events of the early Cold War.

The Russia-Ukraine war greatly affected the global food supply

Russia's invasion devastated Ukraine's agricultural sector, destroying farms, ports, and grain infrastructure and causing over $40B in losses. Disrupted exports fueled global food insecurity, while Moscow leveraged its grain exports to expand influence across the Global South.

The final war between the Persian and Byzantine empires

The Arab conquests of the seventh century, which swept over Egypt, Syria, and Mesopotamia, were made possible by a catastrophic generation-long war between the Byzantine and Persian Empires. That war, in turn, was the last act in a struggle that had gone on for centuries, and shaped the whole subsequent history of the Middle East.

Hitler's 1941 invasion of the USSR doomed Nazi Germany

Hitler unleashed Operation Barbarossa on June 22, 1941, underestimating Soviet resilience, Russian winter, and logistics. His overconfidence—rooted in early victories like France—turned this campaign into a strategic catastrophe, shifting the war’s momentum irreversibly—often cited as his greatest blunder.

What led to the October Revolution?

The 1917 Russian Revolution is actually two separate revolutions. One happened that spring that ended centuries of Tsarist rule and led to the establishment of a provisional government. Another happened that autumn during which the Bolshevik...

The causes of American rebellion were multifaceted

British taxes on colonists to pay for the French and Indian War were just one element. Thousands of miles of separation between London and the Colonies, expanding territories, a distinct Colonial identity, and political conflicts combined to prompt the Revolution.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

Why the 1918 flu killed between 50 and 100 million people

The 1918–1920 flu pandemic (once called, incorrectly, the Spanish flu) killed quickly and in huge numbers, with estimates of the global death toll ranging from 50 to 100 million people. Several factors contributed to the high mortality rate: lack of antibiotics, the global disruption of World War I, and more.

The British Empire, explained

This three-minute 1440 explainer traces the rise of the British Empire, which at its height ruled nearly one in four people—about 500 million—and spanned so many regions that admirers called it “the empire on which the sun never sets.”

Explore an interactive map of battles from the American Revolution, along with detailed summaries of each engagement

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

Poison ivy was sent to Europe in the 1600s as an exotic, ornamental oddity, where it was purposefully grown in the English royal gardens at Kew, the Faculty of Medicine in Paris, and a few other locations.

Fireworks make a loud booming sound after exploding due to air expanding faster than the speed of sound.

See the most iconic photos from four decades of LIFE magazine

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

American dance legend Martha Graham, sometimes called 'the Picasso of dance,' refused to perform at the 1936 Olympics in Berlin and conceived the piece 'Chronicle' in response to the experience.

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.

View the ten deadliest tornadoes in US history.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

The most expensive ad of all time was for Chanel No. 5 perfume and cost roughly $33M to produce in 2004—about $57M in today's dollars.

Waves off the coast of Nazaré, Portugal, can reach over 100 feet and are caused by the area's deep underwater canyon geography

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.