Who participated in the First World War?

After the outbreak of war in August 1914, Britain recruited a huge volunteer citizens' army. In just eight weeks, over three-quarters of a million men in Britain had joined up. Every volunteer had to undergo a series of medical and fitness tests before being accepted as a soldier. 

Pals battalions were a uniquely British phenomenon. Britain was the only major power not to begin the First World War with a mass conscripted army. After the war broke out, it quickly became clear that the small professional British Army was not large enough for a global conflict.

Discover a rich selection of First World War recruitment posters from IWM's collection. 

Before the First World War there had never been compulsory military service in Britain. There were approximately 16,000 British men on record as conscientious objectors (COs) to armed service during the First World War.

Max Plowman (1883-1941) was a British Army officer and writer who served on the Western Front during the First World War. He is perhaps best known for his 1928 memoir of his war experiences A Subaltern on the Somme, published under the pseudonym ‘Mark VII’.

Delving into the IWM film and sound archives, we uncover some incredible true stories of the women who served and worked during the First World War.

Dolly Shepherd had earned a reputation as a daredevil before the First World War - but by the time Armistice Day 1918 arrived, she had demonstrated what women were capable of during war. 

During the First World War, 250,000 Belgians came to Britain fleeing the conflict that had taken over their country. Some of those who came would end up playing an important role in the war effort. 

Though black units played a vital role in Allied victory in the First World War, once the war was over their contribution was deliberately forgotten in an attempt to protect the British Empire. 

In 1915 Britain's War Office, which had initially opposed recruitment of West Indian troops, agreed to accept volunteers from the West Indies. A new regiment was formed, the British West Indies Regiment (BWIR), which served in Europe, the Middle East and Africa.

Soldiers from the Empire and Commonwealth made a significant contribution to the Somme offensive. On 1 July 1916 a battalion from Newfoundland, attacked with the 29th Division, while the 1st Battalion, The Lincolnshire Regiment included a contingent from the Bermuda Volunteer Rifle Corps.

Between 1914 and 1918 more than 120,000 New Zealanders – nearly 20% of the country’s eligible manpower – served overseas with the New Zealand Expeditionary Force, the Royal Navy or units of the British Army.

Explore 12 photographs from IWM's collection of the Indian Army who served during the First World War.

On the night of 21 February 1917, more than 600 men of the South African Native Labour Corps (SANLC) lost their lives in the sinking of the SS Mendi- the largest single loss of life for the non-combatants in the SANLC during the First World War.

In summer 1914 Ireland, then part of the UK, stood on the brink of civil war. Parliament had voted for Home Rule - limited self-government - for Ireland, a controversial and divisive policy. One result of this was that both those in favour of Home Rule and those against it organised their own armed forces: the anti-Home Rule Ulster Volunteer Force and the pro-Home Rule Irish Volunteers.

After the outbreak of the First World War, men flocked to recruiting stations in Ireland. Their motivations were often the same as those who joined up in England, Scotland and Wales: a sense of duty, the belief that the war was a just cause, a desire for adventure, the bonds of friendship and economic reasons.

Over 16 million animals served in the First World War. They were used for transport, communication and companionship. Horses, donkeys, mules and camels carried food, water, ammunition and medical supplies to men at the front, and dogs and pigeons carried messages. 

Animals have served alongside humans in combat for thousands of years, and still do to this day. In war, why would soldiers choose to keep animals around with seemingly no strategic value? Here, we learn the answer to this question, and find out how a meal became a friend, how a bear became an artilleryman and how a penguin became an officer.

First raised in 1916, the Imperial Camel Corps was a camel-mounted infantry force operating in the Middle Eastern and African deserts. The Corps played an integral role in several First World War desert campaigns, including Palestine and Sinai. Here are 10 photos of the Imperial Camel Corps cameliers and their trusty steeds.