There are thought to have been around 40 million casualties as a result of the four-year conflict.
The war also saw the collapse of the some of the great European powers as empires broke-up and smaller states began to establish themselves and expand.
The German, Ottoman, Russian and Austro-Hungarian Empires collapsed and were replaced by states such as Poland, Estonia, Czechoslovakia and Hungary, with much of Europe redrawn along ethnic lines.
The battlefield at Verdun after the major battle there
What is the Armistice and where was it signed?
After four years of fighting, the leaders of the Allied Powers forced a defeated Germany to sign the Armistice aboard French general Ferdinand Foch’s private train in a railway siding in the forest of Compiègne, northern France.
Among the terms that Germany agreed to were the cessation of all hostilities and the withdrawal of troops to behind the Rhine.
What was the Treaty of Versailles?
The Treaty of Versailles was signed after six months of negotiation on June 28, 1919, which ended the state of war between Germany and the Allied Powers.
It ended the state of war between Germany and the Allied Powers but also contained a War Guilt Clause, which burdened Germany with massive reparative costs while stripping them of territory and requiring them to disarm, which some argue lead to the rise of nationalism.
German soldiers bring in Canadian wounded during the Battle of Vimy, France, in 1917
AP
From the outset, Germany had tried to avoid fighting an extended, and costly, war on two fronts as both Russia and France were mobilising troops.
Their original plan of action was to knock France out of the war by focusing power on the Western Front, before heading eastwards to destroy Russia.
To do this Germany intended to rapidly push into Paris, a strategy which required the unconditional right of passage through Belgium.
World War One armistice centenary artwork
But the Belgians resisted this advance, which led to British intervention and a declaration of war on August 4, 1914 following Germany’s refusal to respect Belgium’s decision of neutrality.
Germany was now fighting a fully mobilised Russian army on the east as well as the combined might of Britain, France and Belgium on the Western Front.
US troops advance on a path near the Somme in France, in 1918
AP
Despite capturing several defensive strongholds in France, Germany failed to secure a decisive victory in the west, leading to the German Crown Prince William saying: “We have lost the war. It will go on for a long time but lost it is already.”
In 1917, Russia withdrew from the war after the new Bolshevik government signed the Treaty of Brest-Litovsk, following the October Revolution.
Their withdrawal freed up German soldiers to fight on the Western Front, who soon launched a powerful offensive which pushed back the Allied powers.
But their advance was counteracted by the Hundred Days Offensive, which crippled the Central Powers on the Western Front and eventually ended the war.
In the Middle East, British, French and Russian forces, along with local allies, defeated the Ottoman Empire through a number of offensives and campaigns, culminating in the Battle of Megido in 1918.
Soldiers carry a stretcher through the mud in Belgium in 1917
AP
Soon the German, Ottoman and Austro-Hungrian Empires were all facing revolution, mutiny and unrest, and they signed separate treaties of surrender which divided their lands, erected new governments and imposed harsh punishments.
The defeated Central Powers were made to sign treaties which inflicted upon them similar, yet weaker, punishments, while the political landscape of Europe had become permanently changed.
The fractured Austro-Hungarian, Ottoman and German empires broke up into a succession of smaller states, which allowed for better representation of ethnicities and groups.
While the newly-formed League of Nations served as a global platform of discussion and peacemaker, instead of the private meetings which powers took part in before.
After the signing of the Armistice in November 1918, most soldiers were allowed to return home and those who stayed were not at a significant risk of death.
De-escalation slowly took effect and conferences were held to determine the future of Europe.
How do we mark Remembrance Day, and when is the two-minute silence?
Given that the end of World War One was marked on the 11th hour of the 11th day in the 11th month, November 11 is now recognised each year as Remembrance Day.
Around this time, many people wear poppies and may take part in commemorations and events that remember the people who took part in the war and our armed forces.
Remembrance Sunday, which takes place on November 10 this year, will see vast parades through London to the Cenotaph. It brings together veterans, leaders and people from around the world to come and reflect on the lives lost.
It’s also a reminder of the power of peace, and a lesson from history about the risk of war that will likely resonate even more this year given the current conflicts around the world.
At 11am each year on November 11, a two-minute silence is held to remember the fallen soldiers who gave their lives during WW1. Another is also held at 11am on Remembrance Sunday.
It’s an important moment in UK culture, when a lot of the country comes to a standstill to reflect on the loss of life in war. Other countries in the Commonwealth also mark this Remembrance Day tradition.
