World War I

World War I—also known as the Great War—pitted Germany, Austria-Hungary and the Ottoman Empire against Great Britain, the United States, France, Russia, Italy and Japan. New military technology resulted in unprecedented carnage. By the time the war was over and the Allied Powers claimed victory, more than 16 million people—soldiers and civilians alike—were dead.

Featured Overview

Archduke Ferdinand's assassination caused the outbreak of World War I, but what caused the assassination itself? It may have been something as simple as a wrong turn.

3:14m watch

Battle of the Somme

Royal Engineers No 1 Printing Company/ IWM via Getty Images

Featured Overview

Archduke Ferdinand's assassination caused the outbreak of World War I, but what caused the assassination itself? It may have been something as simple as a wrong turn.

3:14m watch

Start Here

HISTORY: World War I Battles, WWI Timeline

This World War I timeline of battles outlines the most important engagements of the 1914-1918 war, from the first Battle of Mons to the final 1918 armistice.

Beginning of World War I between Austria-Hungary and Serbia: Fighting near the bridge over the Sava River.

When Austria-Hungary declared war on Serbia in 1914, each of their allies quickly joined the fight.

Returning WWI soldiers on board the USS Agamemnon

World War I’s legacy of debt, protectionism and crippling reparations set the stage for a global economic disaster.

WWI Inventions

These World War I inventions made life easier during—and after—the war.

The Harlem Hellfighters

The Harlem Hellfighters

The Harlem Hellfighters were an African-American infantry unit in WWI who spent more time in combat than any other American unit. Despite their courage, sacrifice and dedication to their country, they returned home to face racism and segregation from their fellow countrymen.

6:06 watch

Explore All Related Topics

World War I

In 1997 Dr.Johan Hultin excavated an indigenous village graveyard in hopes to find the cause of Spanish flu but found much more.

3:26m watch

Here are some of the essential items that typical doughboys carried with them on the battlefields of World War I.

Some winged warriors, like the famed Cher Ami, received military honors for their intrepid feats as battlefield messengers.

Ferdinand Foch was a French military leader who served as supreme commander of the Allied armies during the final months of World War I.

Prussian-German field marshal and statesman Paul von Hindenburg (1847 - 1934) in military uniform, circa 1918.

Paul von Hindenburg was a significant and controversial political figure in German history who served as the second president of the Weimar Republic. While some praised him for stabilizing Germany in the wake of World War I sanctions, Hindenburg played a key role in Adolf Hitler’s rise to power.

British Field Marshal Sir John Denton Pinkstone French

Field Marshal Sir John French, Earl of Ypres, served as the commander in chief of the British Expeditionary Forces during World War I.

Portrait of French military commander General Joseph Joffre (1852 - 1931) during the First World War, France, circa 1914. (Photo by PhotoQuest/Getty Images)

Joseph Joffre played a significant role in shaping the outcome of World War I. The commander-in-chief of the French Army became an iconic symbol of French resistance for his defense against the German invasion on the Western Front.

Still from the film "Battle of the Somme," showing British troops.

The carnage of the war was so extreme that historians have had difficulty agreeing on exactly how many people lost their lives.

A German U-boat, circa 1916.

After terrorizing trans-Atlantic ships in World War I, German U-boats grew even more fearsome in World War II.

Battle of Cambrai, World War I, WWI battles

Many of the powers in World War I were competitive in overtaking territories in Europe and Africa.

Brigadier General Billy Mitchell in cockpit of a Thomas Morse Pursuit Plane. Ca. 1910s.

Even though airplanes were a relatively new invention, the race for air superiority started during World War I.

Beginning of World War I between Austria-Hungary and Serbia: Fighting near the bridge over the Sava River.

When Austria-Hungary declared war on Serbia in 1914, each of their allies quickly joined the fight.

Site of the battle of Tannenberg, Germany, August 1914.

The 1914 conflict dealt a defeat so devastating that it drove a Russian general to suicide.

The Germans were the first to successfully weaponize gas in World War I—to horrifying effect.

World War I's Battle of Messines: How Tunnel Blasts Secured Allied Victory

The June 1917 Allied attack involved meticulous planning, tunneling and devastating explosives.

Marcelino Serna came to the U.S. as a undocumented immigrant, and within just a few years, became one of the country's bravest heroes.

1:04m watch

After the Spanish Flu descended on New York City in 1918, its citizens did everything they could to flatten the curve.

1:03m watch

Learn about Hitler's survival during WWI.

3:05m watch

HISTORY: World War I Battles, WWI Timeline

This World War I timeline of battles outlines the most important engagements of the 1914-1918 war, from the first Battle of Mons to the final 1918 armistice.

8 Events That Led to World War I, WWI

Imperialism, nationalistic pride and mutual alliances all played a part in building tensions that would erupt into war.

Learn about the use of poisonous gas during WWI.

2:07m watch

How World War I Eclipsed 1918 Pandemic Memorials

Both World War I and the 1918 influenza pandemic were devastating events in history. So why did memorials for one event overshadow the other?

Why the 1918 Flu Pandemic Never Really Ended

After infecting millions of people worldwide, the 1918 flu strain shifted—and then stuck around.

Why Schools in New York City and Chicago Stayed Open During the 1918 Flu Pandemic

Amid fierce controversy, public health officials in both cities decided children would be better off in classrooms.

Open-Air Schools, 20th century

Intended to curb the spread of tuberculosis, open-air schools grew into a major international movement in the early 1900s.

"Wear a Mask, or Go to Jail" Propaganda Used During the 1918 Pandemic

Cartoons, PSAs and streetcar signs urged Americans to follow health guidelines to keep the pandemic from spreading.

History of Pandemic Advances, 1918 Flu

Diseases have devastated human populations, but they've also inspired social upheaval and innovations.

Doctors, army officers, and reporters wear surgical gowns and masks at a hospital to observe Spanish influenza treatment of patients

Once it was over, no one wanted to talk about it.

1918 Flu Pandemic, World War I hospital

Nations fighting in World War I were reluctant to report their flu outbreaks.

1918 Flu pandemic mask-wearing rules

Most people complied, but some resisted (or poked holes in their masks to smoke).

How the U.S. Pulled Off Midterm Elections Amid the 1918 Flu Pandemic

A lot was on the line, and not just for Democrats in Congress.

After millions perished, people turned to séances, Ouija boards and more to help communicate with their dearly departed.

Convalescent Plasma history

Doctors first tried injecting patients with blood plasma in the early 1900s. The method has been used against diphtheria, the 1918 flu pandemic, measles and Ebola.

Maurice Hilleman

By the time the virus reached the U.S., the country already had a vaccine ready.

How U.S. city officials responded to the 1918 pandemic played a critical role in how many residents lived—and died.

1918 FLu

The first strain of the 1918 flu wasn’t particularly deadly. Then it came back in the fall with a staggering death toll that eclipsed even the casualties of World War I.

Spanish Flu, 1918

Undertakers, gravediggers and casket makers couldn’t keep up with history’s deadliest pandemic.

During the first half of the 20th century, people used a variety of measures—including gargles, masks and signs—to try and avoid catching the flu.

WWI Runners

Runners were more reliable than any other form of communication. But the role was among the war's most dangerous.

Kaiser Wilhelm

Under the Treaty of Versailles, the German emperor was supposed to be tried as a war criminal. Why wasn't he?

After the Treaty of Versailles called for punishing reparations, <br>economic collapse, the rise of Naziism, and another world war thwarted Germany's ability to pay.

Treaty of Versailles

Some disarmed the German military, while others stripped the defeated nation of territory, population and economic resources, and forced it to admit responsibility for the war and agree to pay reparations.

In 1918 the Spanish Flu killed at least 50 million people around the world and was the second deadliest plague in history–after, well, the plague in the 1300s. But how exactly did a flu virus cause such massive death and destruction across the world?

5:42m watch

Digitally colorized photographs from a century ago help bring "The Great War" to life.

USS San Diego

The sinking of the USS San Diego was a mystery for 100 years.

On November 11, 1918, World War I finally came to an end after four-plus years of combat. Armistice Day was wildly celebrated throughout the world, and in this rare footage, we see how New York, Washington D.C. and Paris took to the streets with pure joy.

3:28m watch

Henry Gunther

The six-hour delay between the armistice signing and World War I’s official end cost the lives of nearly 3,000 soldiers, including one American in the war’s final minute.

People celebrate the fake WWI armistice

Four days before the actual end of World War I, a false report misled the country and set off wild celebrations.

WWI Dogs

From killing rats in the trenches to locating the wounded to keeping an eye out for the enemy, dogs served loyally at the side of soldiers and medics in World War I.

General Weygand, Admiral Wemyss and Marshall Foch

Both sides had suffered too much to continue, but Germany would be left battered by harsh terms.

1914 Christmas Truce

Over Christmas 1914, singing and soccer broke out between British and German forces.

WWI Inventions

These World War I inventions made life easier during—and after—the war.

Archduke Ferdinand's assassination caused the outbreak of World War I, but what caused the assassination itself? It may have been something as simple as a wrong turn.

3:14m watch

World War IArchduke Franz Ferdinand and his wife assassinated in Sarajevo, Yugoslavia on June 28, 1914. (Photo by Keystone-France/Gamma-Rapho via Getty Images)

The seeds of the devastating conflict had been planted long before the assassination of Archduke Franz Ferdinand.

Public Domain

Now a multibillion-dollar, nip-and-tuck industry, modern plastic surgery arose a century ago to reconstruct the faces of soldiers disfigured on World War I battlefields.

Franz Ferdinand, archduke of Austria, and his wife Sophie riding in an open carriage at Sarajevo shortly before their assassination.

The assassination of Franz Ferdinand might not have happened but for an odd coincidence that placed him right in front of his assassin’s gun.

Harlem Hellfighters

Blue clouds of poisonous gas. Relentless shelling and machine gun fire. Horace Pippin's art-filled journals recorded life in ‘them lonely, cooty, muddy trenches.'

German General Alfred Schlieffen, author of the Schlieffen Plan for the defeat of Russian and France. (Credit: Universal History Archive/Getty Images)

The Schlieffen Plan, devised a decade before the start of World War I, was a failed strategy for Germany to win World War I.

The bodies of the British soldiers lying dead in their trench during the Battle of the Somme, 1916. (Credit: Mondadori Portfolio/Getty Images)

The Battle of the Somme was one of the largest battles of World War I, and among the bloodiest in all of human history.

Love letters written by poet Rupert Brooke, to his sweetheart Phyllis Gardner, on display at the British Museum in London. (Credit: Matthew Fearn/PA Images/Getty Images)

World War I altered the world for decades, and writers and poets reflected that shift in literature, novels and poetry.

U.S. Military veteran and amputee Lloyd Epps after doctors serviced his prosthetic leg at the Veterans Administration (VA), hospital in Manhattan, New York City, 2014. (Credit: John Moore/Getty Images)

The very existence of the V.A.—which began in 1930—marked a change in how Americans perceived the people who fought its wars.

Trenches—long, deep ditches dug as protective defenses—are most often associated with World War I, and the results of trench warfare in that conflict were hellish indeed.

The sinking of Lusitania by a German submarine off the Old Head of Kinsale, Ireland, 1915. The tragedy killed 128 US citizens, helping bring the US into World War I. (Credit: Three Lions/Getty Images)

A German U-boat torpedoed the British-owned steamship Lusitania, killing 1,195 people including 128 Americans, on May 7, 1915. The disaster set off a chain of events that led to the U.S. entering World War I.

Franz Ferdinand, archduke of Austria, and his wife Sophie riding in an open carriage at Sarajevo shortly before their assassination.

The causes of World War I have been debated since it ended—but the assassination of Archduke Franz Ferdinand was an early catalyst.

A German drawing of a submerged U boat in British waters during World War One. (Credit: Classic Image/Alamy)

How a secret team of British divers hunted codes from German shipwrecks.

Check out six fun facts about the history of tanks.

0:39m watch

See the heroes of the 1918 Spanish flu pandemic in color.

The League of Nations

The League of Nations, a global diplomatic group developed after World War I to solve disputes before they erupted into open warfare, had failed by 1940.

Crowds along Fifth Avenue in New York City celebrated Armistice Day in November 1918.

The United States entered World War I in 1917, following the sinking of the British ocean liner Lusitania and the shocking discovery of the Zimmermann telegram.

These five pooches are living proof that dogs truly are a man’s best friend.

Arthur Zimmermann, circa 1910.

The explosive document helped speed America’s entry into World War I.

Mark I Tank at Battle of the Somme

It was a century ago that a staple of modern warfare—the tank—first made its combat debut at the Battle of the Somme.

Manfred von Richthofen—better known as the “Red Baron”—was the top scoring flying ace of World War I, with 80 aerial victories between September 1916 and his death in April 1918.

Hand colored postcard of Mata Hari performing , 1907

Once Europe’s most prominent striptease performer, Dutch dancer Mata Hari was executed by a French firing squad after she was found guilty of spying for the Germans during World War I.

An explosion that initially looked like an accident, turned out to be an act of sabotage.

Explore 10 surprising facts about the bloodiest encounter of World War I.

There are a number of theories, including ones that involve dust and clay.

Explore 10 surprising facts about one of the longest and most brutal campaigns of World War I.

Explore eight of the most famous chroniclers of the “War to End All Wars.”

The 1918 influenza pandemic did not, as many people believed, originate in Spain.

Sergeant Henry Johnson of the 369th Colored Infantry was awarded the Croix de Guerre for bravery during an outnumbered battle with German soldiers.

Private Henry Johnson, a member of the renowned all-Black unit, fought off nearly two dozen German soldiers during World War I.

The British pet purge

Learn the stories behind eight of history’s most outside-the-box wartime cutbacks.

Get the story behind the ill-fated British ocean liner.

Troops land at Anzac Cove in the Dardanelles during the battle between Allied forces and Turkish forces at the Gallipoli Peninsula for access to the strategic Sea of Mamora and eventually to Constantinople (Istanbul). In February 1915 Turkish mines sank 6 British battleships, causing the naval assault on the Dardanelles to stall. A second Allied landing at Gallipoli failed in August and British forces evacuated Gallipoli in November 1915. (Photo by © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images)

Get the facts on the epic World War I struggle.

Look back at the moment when the holiday spirit sparked impromptu ceasefires along World War I’s Western Front.

In the years leading up to WWI, a series of agreements between the powers of Europe helped determine where and when battlelines were drawn.

2:47m watch

Panorama of the Battle of the Marne in 1914 with Joffre, Fuebssam 20 Eme Siecle, Museum of the two World Wars in Paris, France,. (Photo by: Christophel Fine Art/Universal Images Group via Getty Images)

Look back at the bloody fight that saved Paris and changed the course of World War I.

The Harlem Hellfighters were an African-American infantry unit in WWI who spent more time in combat than any other American unit. Despite their courage, sacrifice and dedication to their country, they returned home to face racism and segregation from their fellow countrymen.

6:06m watch

World War IArchduke Franz Ferdinand and his wife assassinated in Sarajevo, Yugoslavia on June 28, 1914. (Photo by Keystone-France/Gamma-Rapho via Getty Images)

On the eve of the assassination’s centennial, find out how a teenage Serbian nationalist provided the spark for World War I.

Before London was blitzed in World War II, massive German zeppelins rained bombs and terror upon the British capital in World War I.

Your Victory Garden WWII poster

During both World Wars, America's agricultural production became a powerful military tool.

A look back at the legacy of World War I nearly 100 years after the conflict began.

2:29m watch

War Ration Book, food rationing WWII

World War I Following nearly three years of intense combat since the onset of World War I, America’s allies in Europe were facing starvation. Farms had either been transformed into battlefields or had been left to languish as agricultural workers were forced into warfare, and disruptions in transportation made the distribution of imported food extremely […]

Along with several other English colonies, Australia and New Zealand entered World War I shortly after the British Empire declared war on Germany in August 1914. Aussies and Kiwis volunteered to serve by the thousands, and most were shipped to Egypt for training in late 1914. The combined Oceanic force was originally known as the […]

Poppies are pegged on the wall bearing the World War I dead soldiers' names, at the Australian War Memorial in the northern French city of Villers-Bretonneux, commemorating are the ill-fated landing of the Australian and New Zealand Army Corps (ANZAC) at Gallipoli in World War I.

An art historian is leading a campaign to catalogue, and hopefully preserve, America’s World War I memorials.

U.S. forces pinned down in the Argonne Forest.

From a balloon-busting fighter ace and a Navy escape artist to one of the Marine Corps’ most legendary sergeants, meet six servicemen who distinguished themselves on the battlefields of World War I.

These deadly German submarines dominated the waters in both WWI and WWII.

1:59m watch

German fighter pilot Manfred Baron of Richthofen. Photography. around 1916.

The skies over World War I-era Europe served as a brutal testing ground for manned aircraft. Though limited by their primitive machines, these “Knights of the Sky” went on to achieve some of the war’s most extraordinary—and often downright suicidal—feats of heroism. Get the facts on six of the Great War’s most celebrated airborne daredevils.

Thousands of miles of trenches were built during World War I and, for the soldiers living in them, their day-to-day life was nothing short of horrific.

3:14m watch

Arthur Zimmermann (1864-1940) who served as State Secretary for Foreign Affairs of Germany (1916-1917)

Most historians agree that American involvement in World War I was inevitable by early 1917, but the march to war was no doubt accelerated by a notorious letter penned by German foreign secretary Arthur Zimmermann. On January 16, 1917, British code breakers intercepted an encrypted message from Zimmermann intended for Heinrich von Eckardt, the German […]

Did you know that the first-ever tanks, chemical weapons and blood banks were introduced during World War I? Get all the facts behind the conflict known as the "war to end all wars."

2:15m watch

HISTORY: World War I Battles, WWI Timeline

The short answer is no, though it’s hard to pinpoint precisely when the World War I and World War II—or First World War and Second World War—monikers arose. During World War I, of course, nobody knew that a second global conflict would follow closely on the heels of the first, so there was no need […]

In a Mail Call video, R. Lee Ermey answers a question from Mark of Kansas who wants to know what was in a World War I backpack. Ermey reveals that on top of all the other hardships WWI soldiers had to endure, their backpacks proved to be another annoyance. Men from the Great War Historical Society strapped on the WWI packs and completed some drills; by the end, they definitely felt the WWI soldiers pain. The bottom section of the backpack, known as the diaper, was detachable and carried the soldiers blanket, shelter half, and shelter half pole and pins. On the belt youd find ammo, a first aid kit, a canteen cover, and a canteen and cup. Inside the flaps were a baking tin, a condiment can, and boxes of bread rations. Also inside the flaps were a towel, soap dish, shaving kit, handkerchief, foot powder, and extra socks. Attached to the outside were the bayonet, shovel, trenching tool, and a mess kit. The entire weight of the pack lies entirely on the soldiers shoulders, making it very uncomfortable. If a soldier wanted to get anything out of his pack, he would have to stop, unravel everything, get what he needs, and then pack everything back up. Due to the placement of the bayonet, most soldiers would have to have a buddy put it back for them.

2:00m watch

After two years of trench warfare, the Allies attempt to break through German lines on the Western Front. The ensuing battle will last for months and result in more than one million casualties.

1:36m watch

An ill-fated assault on Turkish forces leads to 500,000 casualties in World War I.

1:38m watch

After the repeated sinking of American ships, the President declares war. Historic film footage shows some of the first naval battles.

2:27m watch

When Germany torpedoes a British passenger ship believed to be smuggling arms, anger at the resulting American deaths increases pressure on President Wilson to enter World War I.

2:04m watch

In this video clip of History's Mail Call, host R. Lee Ermey takes a look at how gasmasks work and explains why those sold in surplus stores are not worth the money. Military gasmasks will save your life if they are made and worn properly. When poisonous fumes enter the mask it passes through a filter with a dense layer of carbon and thick padded air cleaner. It is then cleaned and provides fresh air to the soldier or person wearing the mask.

3:32m watch

German resentment over harsh peace terms leads to a rise in nationalist sentiment and the eventual rise to power of Adolf Hitler.

1:56m watch

Although best known for its role in the long slog of World War I, trench warfare actually got its start on the battlefields of the American Civil War. Find out how new weapons and technology played a part in both its development and destruction.

1:15m watch

PERTH, AUSTRALIA - MAY 20: Naval Pallbearers carry the coffin of Mr Claude Choules from the church during the funeral service on May 20, 2011 in Perth, Australia. At the time of his death, Mr Choules was the last known WW1 combat veteran, the last known veteran to have served in both world wars and at 110, the oldest living Australian. Choules was born in the United Kingdom and served for the both the Royal Navy and Royal Australian Navy. (Photo by Paul Kane/Getty Images)

Claude Choules, a resident of Australia who also served during World War II, died Thursday at 110.

Spanish Flu Virus

The Spanish flu pandemic of 1918, the deadliest in history, infected an estimated 500 million people worldwide—about one-third of the planet’s population—and killed an estimated 20 million to 50 million victims, including some 675,000 Americans.

Armenian Genocide: Women and children rescued by Levon Yotneghperian, circa 1919.

The Armenian genocide was the systematic killing and deportation of millions of Armenians by Ottoman Empire Turks from 1915-1920, during and after World War I.

Kaiser Wilhelm II, Emperor of Germany and King of Prussia, late 19th-early 20th century. Wilhelm (1859-1941), was the last German emperor and king of Prussia.

Wilhelm II (1859-1941) was the last German kaiser (emperor) and king of Prussia from 1888 to 1918, and one of the most recognizable public figures of World War I (1914-18). He gained a reputation as a swaggering militarist through his speeches and ill-advised newspaper interviews.

An illustration of the sinking of the British ocean liner RMS Lusitania, torpedoed by German U-boat U-20 off the old head of Kinsale, Ireland.

On May 7, 1915, less than a year after World War I (1914-18) began in Europe, a German U-boat torpedoed and sank the RMS Lusitania, a British ocean liner en route from New York to Liverpool, England. More than 1,100 crew and passengers died, including more than 120 Americans.

HISTORY: The Battle of the Somme

The Battle of the Somme was a deadly Allied offensive against German forces along the Western Front of World War I, near the Somme River in France.

MANFRED von RICHTHOFEN (1892-1918) aka 'the Red Baron'

Who was the Red Baron? Baron Manfred von Richthofen was born on May 2, 1892, into an affluent family of Prussian nobles in what is now Poland. He enjoyed a privileged upbringing and spent his youth hunting and playing sports before being enrolled in mil...

A stereoscopic image of Indian troops on W Beach on Cape Helles, where stores are being unloaded during the Gallipoli Campaign, Gallipoli peninsula, Turkey, World War I, 1915.

In the Gallipoli Campaign of World War I, British, French, Australian and New Zealand troops failed to take the Gallipoli Peninsula from German-Turkish forces.

Dardanelles Campaign: Background As the only waterway between the Black Sea in the east and the Mediterranean Sea in the west, the Dardanelles was a much-contested area from the beginning of World War I. The stakes for both sides were high: British cont...

First two pages of Brest-Litovsk Peace Treaty between Soviet Russia and Germany, Austria-Hungary, Bulgaria and Turkey, ending their participation in World war One. March 1918. (Photo by Universal History Archive/Universal Images Group via Getty Images)

The Treaties of Brest-Litovsk was a seires of treaties Russia signed with the Central Powers ending its participation in WWI.

This World War I siege stemmed from German General Erich von Falkenhayn’s edict to elicit major bloodshed from the French defense of the fortress complex around Verdun. German forces advanced quickly in February 1916, claiming Fort Douaumont and Fort Va...

"I Have a Rendevous with Death."FRANCE - CIRCA 1916: German troops advancing from their trenches. (Photo by Buyenlarge/Getty Images)

World War I started in 1914, after the assassination of Archduke Franz Ferdinand, and ended in 1918. During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central Powers) fought against Great Britain, France, Russia, Italy, Romania, Japan and the United States (the Allied Powers). World War I saw unprecedented levels of carnage and destruction due to new military technologies and the horrors of trench warfare.

HISTORY: Treaty of Versailles

The Treaty of Versailles was signed in 1919 and set harsh terms for Germany’s surrender to Allied powers after World War I, setting the stage for World War II.

HISTORY: John J. Pershing

U.S. Army general John J. Pershing (1860-1948) commanded the American Expeditionary Force (AEF) in Europe during World War I. The president and first captain of the West Point class of 1886, he served in the Spanish- and Philippine-American Wars and was tasked to lead a punitive raid against the Mexican revolutionary Pancho Villa.

Erich Ludendorff was a prominent general and war hero who played a crucial role in shaping and overhauling Germany’s World War I tactics. His innovative approaches to modern warfare left a lasting impression, but controversy surrounds him due to his association with Adolf Hitler and his support of the Nazi Party.