The stabilization of the front in the first months of the conflict led the armies to try to reinforce their positions. The sappers set to work and began digging trenches, building precarious underground shelters, filling them with earthbags and barbed wire. They laid new weapons ready to receive the enemy, while bringing in heavy and semiheavy artillery to punish the enemy positions from a distance. And thousands and thousands of men on both sides were ordered to crouch in those unhealthy holes and await orders.

And so months passed between orders, attacks and counterattacks, mustard gas, shells and almost continuous bombardment, without being able to raise their heads, crouched like animals.

The First World War, previously called the Great War, was a worldwide military conflict, although centered in Europe, which began on July 28, 1914 and ended on November 11, 1918, when Germany accepted the conditions of the armistice of November 11, 1918.

It received the qualification "worldwide" because all the great industrial and military powers of the time were involved, divided into two alliances.20 On the one hand, the Triple Alliance formed by the Central Powers: the German Empire and AustriaHungary. Italy, which had been a member of the Triple Alliance along with Germany and AustriaHungary, did not join the Central Powers, since Austria, contrary to the agreed terms, was the aggressor nation that triggered the conflict.21 On the other hand was the Triple Entente, formed by the United Kingdom, France and the Russian Empire. Both alliances underwent changes and several nations would end up joining the ranks of one side or the other as the war progressed: Italy, the Empire of Japan and the United States joined the Triple Entente, while the Ottoman Empire and the Kingdom of Bulgaria joined the Central Powers. More than 70 million soldiers, of which 60 million were Europeans, mobilized and fought in what was then the largest war in history.2223

Until the beginning of the Second World War, this war was called "Great War" or "World War",24​25​26​ the latter expression that began to be used in Germany from its beginning (Weltkrieg), although it only became general in France (Guerre Mondiale) and in the United Kingdom (World War) in the 1930s, while in the United States the name was imposed after its intervention in 1917,27 since there it was known as "European War ».28​

Although the imperialism that the powers involved had been developing for decades was the main underlying cause, the trigger for the conflict occurred on June 28, 1914 in Sarajevo with the assassination of Archduke Franz Ferdinand of Austria,2930 at the hands of Gavrilo Princip, a young Serbian nationalist. 31 32 This event sparked a diplomatic crisis when AustriaHungary gave the Kingdom of Serbia an ultimatum and invoked the various international alliances forged over the previous decades. Within weeks, all the major European powers were at war, and the conflict spread to many other geographic areas.

On July 28, the AustroHungarians began hostilities with an attempted invasion of Serbia.3334 While Russia was mobilizing, Germany invaded Belgium, which had declared itself neutral, and Luxembourg on its way to France. The violation of Belgian sovereignty led the United Kingdom to declare war on Germany. The Germans were stopped by the French a few kilometers from Paris, and a war of attrition began where the trench lines would barely change until 1917. This front is known as the western front. On the eastern front, the Russian army achieved some victories against the AustroHungarians, but was stopped by the Germans in their attempt to invade East Prussia. In November 1914, the Ottoman Empire entered the war, which meant the opening of different fronts in the Caucasus, Mesopotamia and Sinai. Italy and Bulgaria joined the war in 1915, Romania in 1916, and the United States in 1917.

After years of relative stalemate, the war began its denouement in March 1917 with the fall of the Russian government after the February Revolution and the signing of a peace agreement between revolutionary Russia and the Central Powers after the October Revolution, in March 1918. On November 3, 1918, the AustroHungarian Empire signed an armistice. Following a major German offensive in early 1918 along the entire length of the Western Front, the Allies drove the Germans back in a series of successful offensives. Germany, in the midst of the revolution, requested an armistice on November 11, 1918, ending the war with an Allied victory.