▲German soldiers in a railway goods wagon on the way to the front. Most combatants adopted a cheerful optimism early on in the war, as all sides expected the conflict to be a short one.

▲The declaration of war sparked patriotic fervor and a real sense of duty among the Allied Powers. Pictured is a busy military recruitment office in Melbourne.

▲Similarly, the Central Powers began calling up civilians, drawn from the vast Ottoman Empire. Pictured is a military recruitment outpost near Tiberias, in modern-day Israel.

▲Despite a previous alliance with Germany and Austria-Hungary, Italy eventually joined the war on the side of the Allied Powers. The photograph shows a pro-war demonstration in Bologna.

▲The 'Lord Kitchener Wants You' recruitment poster is one of the most iconic and enduring images of the conflict. Kitchener was the British Secretary of State for War.

▲A refugee transport train from Serbia arrives in the Austrian town of Leibnitz. Note how well-dressed these displaced people are.

▲The graffiti painted on this French gate marks the home of a known spy and traitor. The word 'Boche' was used during the First World War as an offensive term for a German.

▲As a member of the Triple Entente (alliance), Russia fought against the Central Powers. Here, Russian troops gather in a forest trench during the Battle of Sarikamish.

▲The Battle of Frontiers was a series of battles that eventually saw Franco-British forces driven back by the Germans. Pictured are Belgian Carabiniers with dog-drawn machine gun carts during the retreat to Antwerp.

▲The Royal Navy battlecruiser HMS Inflexible standing by to pick up survivors from the German cruiser SMS Gneisenau during the Battle of the Falkland Islands.

▲A horse is landed from a British military transport ship at Boulogne. Horses were heavily used during the conflict, and by the end of the war it's estimated that eight million of these animals, plus countless mules and donkeys, had been killed.

▲British troops of the IX Corps on the beach after landing at Suvla on the Aegean coast of the Gallipoli peninsula.

▲Australian troops scrambling up a hill towards a Turkish trench during the ill-fated Gallipoli Campaign.

▲French troops march under a Mediterranean sun after landing at Moudros, Lemnos island, during the Gallipoli Campaign.

▲Field Marshal Lord Kitchener (center) and Lieutenant-General William Birdwood (left) visiting troops during the Battle of Gallipoli. The bloody campaign ultimately resulted in victory for Ottoman forces.

▲The ruins of Ypres market square during the Second Battle of Ypres. The battle is notable for the introduction of gas by the German army as a new and deadly weapon.

▲A rare color image taken during the First World War depicts Austrian prisoners of war in Olonets, a governorate of northwestern Imperial Russia.

▲Bulgarian soldiers peer skywards as they prepare to open fire against an incoming airplane.

▲The British Army also used gas during the First World War. The threat of a gas attack was so great that even during periods of rest and relaxation soldiers had to be on their guard. Pictured is a football team of British combatants with gas masks on the Western Front.

▲Men of the 10th (Service) Battalion, East Yorkshire Regiment of the 31st Division marching towards the front line on the Somme. Note the long hairstyle of the soldier at the front of the column.

▲A group of "Tommies" (soldiers) Royal Irish Rifles, their smiling faces masking a collective apprehension, during the first day on the Somme.

▲The now famous image of the cataclysmic explosion of a mine set beneath the German frontline fortification of Hawthorn Ridge Redoubt on the Somme.

▲One of the very first frontline combat photographs to be published, this image shows soldiers of the Wiltshire Regiment going "over the top" during the Battle of the Somme.

▲French reserves on horseback crossing a river on their way to Verdun.

▲The Battle of Verdun was the largest and longest battle of the conflict. An estimated 976,000 French and German troops lost their lives during the 300 days it took for the French to finally secure a victory.

▲Workers at the British War Library prepare book parcels for dispatch to British soldiers wounded on the front.

▲Canadian troops advancing behind a British Mark II tank at the Battle of Vimy Ridge. The Canadian Corp were singled out for its technical and tactical prowess, meticulous planning, and stubborn resolve.

▲A young German Sommekämpfer pauses during a lull in the Somme campaign.

▲Back at the home front, it's play hour at a nursing club for "Tommy Atkins Jnr," the collective name given to children of British soldiers during World War One. "Tommy" was a slang term for a common British soldier.

▲With the war in full swing, Britain's King George V (front left) and a group of officials inspect a British munitions factory.

▲A British artillery battery of 16 heavy guns on Mount Scopus during preparations for the Battle of Jerusalem, part of the Sinai and Palestine campaign.

▲US President Woodrow Wilson speaking before Congress, announcing the break in official relations with Germany on February 3, 1917. America subsequently entered the conflict on April 6.

▲After America's entry into the war, young men from across the country eagerly began signing up for the armed forces. Here is a small group registering for conscription in New York City.

▲A Sopwith Camel, a single-seat biplane in service with the Royal Air Force. The average life expectancy of a British pilot on the Western Front was 93 flying hours.

▲British prisoners, seemingly resigned to their fate, guarded by Ottoman forces after the First Battle of Gaza.

▲Soldiers of an Australian 4th Division field artillery brigade on a duckboard track passing through the shattered remains of Chateau de Hoog, near Ypres.

▲British soldiers caught in striking silhouette moving carefully forward during the Battle of Broodseinde, near Ypres.

▲The Battle of Passchendaele was another devastating and futile confrontation. Pictured is an aerial view of Passchendaele village before the battle...

▲... and the same scene afterwards. The battle claimed 13,000 Allied lives, including 2,735 New Zealanders—one of the worst days in New Zealand military history!

▲Rigid airships known as Zeppelins were used by Germany during the war as bomber and scout aircraft. Pictured is the crater of a Zeppelin bomb in Paris.

▲Ottoman Sultan Mehmed V greeting the German Emperor Wilhelm II upon his arrival in Constantinople.

▲The Hindenburg Line, a German defensive position on the Western Front, seen from the air.

▲Several of the photographs in this gallery were taken by Ernest Brooks, the first British official photographer to be appointed to cover the conflict. He's seen here carrying a Goerz Anschutz folding plate camera. Brooks served as a photographer on the Western Front from March 1916 to early 1919.

▲The use of gas during the First World War was a controversial measure, with all the major powers deploying lethal agents, including phosgene, chlorine, and mustard gas. Here British 55th Division soldiers blinded by tear gas during the Battle of Estaires line up to be treated.

▲As the war progressed along the Western Front, an increasing amount of German soldiers were captured and detained as prisoners of war.

▲No hostilities took place on American soil. Instead, the domestic war effort concentrated on propping up the home front. Pictured are female American college students at a farm, where they are working as replacements for men called up to the military.

▲Once again, wounded British and German troops found themselves rubbing shoulders, this time in the streets of St. Quentin after the Second Battle of the Somme.

▲The wreckage of a two-seat German Hannover biplane brought down in the Argonne by American machine gunners between Montfaucon and Cierges.

▲American soldiers entrenched on the Piave front hurling hand grenades into the Austrian trenches.

▲German soldiers resting while others continue the advance through a featureless wasteland during the Second Battle of the Somme.

▲Allied troops parade through Vladivostok in armed support of the anti-communist White Army, September 1918

▲A Canadian poet, physician, author, artist, and solider, McCrae penned the now famous poem 'In Flanders Fields,' which references the red poppies that grew over the graves of fallen soldiers. Today the poppy is one of the world's most recognized memorial symbols for soldiers who have died in conflict.

▲Sassoon saw action on the Western Front and was recommended for the Victoria Cross. Between feats of incredible bravery he wrote poetry, describing the horrors of trench warfare in chillingly moving prose.

▲Lawrence joined the Arab revolt against the Ottoman Empire during the First World War, and was instrumental in the 1918 conquest of Palestine. This period of his life was famously depicted in the epic war drama 'Lawrence of Arabia' (1962).

▲French general Ferdinand Foch (second from right), pictured outside the carriage in Compiègne after drawing up the Armistice of November 11, 1918 that ended fighting on land, sea, and air initially between the Allies and Germany.

▲How one American newspaper reported the historic event to its readers.

▲Across the French capital Parisians in their thousands celebrated the announcement of the Armistice.

▲Still in the field but with all guns silent, soldiers of US 64th Regiment, 7th Infantry Division, celebrate the news of the Armistice.

▲Women of the Women's Royal Australian Naval Service (WRANS), waving flags and smiling on Armistice Day in London.

▲Crowds filling streets surrounding City Hall, Philadelphia, Pennsylvania in celebration of the momentous occasion.

▲The German submarine U-155 exhibited as a trophy near Tower Bridge in London after the Armistice.

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An innocuous portrait of a group of German infantryman recuperating in a military hospital taken towards the end of the war. Look closely. The man standing back row, second from right is lance corporal Adolf Hitler. Twenty-one years later, Chancellor Adolf Hitler would plunge the world into a second, even more catastrophic war. A warning from history!

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Austria-Hungary invaded Serbia at the outset of the conflict. After the Battle of Kosovo, in which Bulgarian forces also played a major part, the Serbs were forced to retreat through Albania in terrible winter conditions.

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Injured men and walking wounded at the side of a road after the Battle of Menin Road, Ypres.

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The assassination of Archduke Franz Ferdinand and his wife Sophie by Gavrilo Princip precipitated a series of events that eventually led to the outbreak of the First World War. This photograph was taken as they got into the car that they were assassinated in.

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The dreadful conflict that was the First World War is often being brought back into stark focus as humanity ponders the futility of the first truly global confrontation and the senseless battles that took the lives of so many millions. This collection of amazing photographs revisits the Western Front, the home front, and beyond, and captures the faces and places caught up in this momentous, era-defining event.

Click the gallery for a pictorial journey through the Great War.