The soldiers of the war were initially volunteers, except for Italy, but increasingly were conscripted into service. Britain's Imperial War Museum has collected more than 2,500 recordings of soldiers' personal accounts and selected transcripts, edited by military author Max Arthur, have been published. The museum believes that historians have not taken full account of this material and accordingly has made the full archive of recordings available to authors and researchers. Surviving veterans, returning home, often found that they could only discuss their experiences amongst themselves. Grouping together, they formed "veterans' associations" or "Legions", as listed at Category:Veterans' organizations.

Prisoners of world war I

About 8 million men surrendered and were held in POW camps during the war. All nations pledged to follow the Hague Convention on fair treatment of prisoners of war. A POW's rate of survival was generally much higher than their peers at the front. Individual surrenders were uncommon. Large units usually surrendered en masse. At the Battle of Tannenberg 92,000 Russians surrendered. When the besieged garrison of Kaunas surrendered in 1915, some 20,000 Russians became prisoners. Over half of Russian losses were prisoners (as a proportion of those captured, wounded or killed); for Austria-Hungary 32%, for Italy 26%, for France 12%, for Germany 9%; for Britain 7%. Prisoners from the Allied armies totalled about 1.4 million (not including Russia, which lost 2.-3.5 million men as prisoners.) From the Central Powers about 3.3 million men became prisoners.

Germany held 2.5 million prisoners; Russia held 2.9 million; while Britain and France held about 720,000. Most were captured just prior to the Armistice. The U.S. held 48,000. The most dangerous moment was the act of surrender, when helpless soldiers were sometimes gunned down. Once prisoners reached a camp, in general, conditions were satisfactory (and much better than in World War II), thanks in part to the efforts of the International Red Cross and inspections by neutral nations. Conditions were terrible in Russia, starvation was common for prisoners and civilians alike; about 15–20% of the prisoners in Russia died. In Germany food was scarce, but only 5% died.

The Ottoman Empire often treated POWs poorly. Some 11,800 British Empire soldiers, most of them Indians, became prisoners after the Siege of Kut, in Mesopotamia, in April 1916, 4,250 died in captivity. Although many were in very bad condition when captured, Ottoman officers forced them to march 1,100 kilometres (684 mi) to Anatolia. A survivor said: "we were driven along like beasts, to drop out was to die." The survivors were then forced to build a railway through the Taurus Mountains.

In Russia, where the prisoners from the Czech Legion of the Austro-Hungarian army were released in 1917 they re-armed themselves and briefly became a military and diplomatic force during the Russian Civil War.

While the Allied prisoners of the Central Powers were quickly sent home at the end of active hostilities, the same treatment was not granted to Central Power prisoners of the Allies and Russia, many of which had to serve as forced labor, e.g. in France until 1920. They were only released after many approaches by the ICRC to the Allied Supreme Council. There were still German prisoners being held in Russia as late as 1924.

Military attachés and war correspondents

Military and civilian observers from every major power closely followed the course of the war. Many were able to report on events from a perspective somewhat akin to modern "embedded" positions within the opposing land and naval forces. These military attachés and other observers prepared voluminous first-hand accounts of the war and analytical papers.

For example, former U.S. Army Captain Granville Fortescue followed the developments of the Gallipoli campaign from an embedded perspective within the ranks of the Turkish defenders; and his report was passed through Turkish censors before being printed in London and New York. However, this observer's role was abandoned when the U.S. entered the war, as Fortescue immediately re-enlisted, sustaining wounds at Montfaucon d'Argonne in the Meuse-Argonne Offensive, September 1918.

In-depth observer narratives of the war and more narrowly focused professional journal articles were written soon after the war; and these post-war reports conclusively illustrated the battlefield destructiveness of this conflict. This was not the first time the tactics of entrenched positions for infantry defended with machine guns and artillery became vitally important. The Russo-Japanese War had been closely observed by Military attachés, war correspondents and other observers; but, from a 21st Century perspective, it is now apparent that a range of tactical lessons were disregarded or not used in the preparations for war in Europe and throughout the Great War.