On July 28 1914, a month after the assassination of Archduke Franz Ferdinand in Sarajevo, through a telegram Austria-Hungary officially declares war on Serbia, held responsible for the attack, so the First World War broke out which in just four years caused more than 17 million deaths. The assassination of Franz Ferdinand was only the spark that triggered the war, because there were deep tensions at international level, which were however destined to explode.
To explain the reasons that led to the First World War we have to go far back in history. In 1702-1704 we have the first betrayal of European peace created with the conference of Westfalia, with the war for succession in Spain. From which arose: the peace of Utrecht, and the peace of Raastad. These two treaties were inspired by the new principle of "Balance of Power", of which Britain was the guarantor, even if its purpose was only to be able to oppose French expansionism. In fact, we see that in that period France, in order to justify its expansionist acts, appealed to the so-called Reason of State, a principle which had also been taken up in its Revolution. The concept of the Reason of State refers to the principle according to which, in order to achieve national interest, it is allowed to pursue any policy, without taking into account ethical, religious or moral values. At the beginning of the 1800s, we see that France had serious expansionist aims, which were initially opposed mainly by Britain, and Russia, them also brought Austria and Prussia to their side to defend themselves. Thus, forming a compact blockade against France.
Having won the war against France, in 1815 we have one of the most important events in history, the Congress of Vienna, which led to a prosperous period of peace for Europe until the beginning of the 1900s. The congress appealed to two basic principles. The first was the principle of legitimacy: to obtain order and balance it was necessary for all the sovereigns who had been ousted by Napoleon to return to their throne. And the second was that of shared responsibility: the principles resulting from this congress should have guaranteed European peace, which depended on how the powers would defend these principles over time. In the years following the Congress in Vienna, however, the situation was very different from what had been envisaged. France returned to the field to conquer the territories it had lost, and Realpolitik replaced the Rason of State, two great commanders were bearers Bismark and Napoleon III. The idea was that relations between states had to be determined by strength.
Therefore, the geopolitical system had changed: those alignments between powers began to emerge, which increasingly highlighted the enmity between France and Germany, and the constant hostility between Russia and the Austro-Hungarian Empire. These precarious balances soon turned into an arms race. This suggests that already at the end of the 1800s the powers were ready for a possible war.
Two blocs of alliances began to form, Germany and the Austro-Hungarian Empire signed a defensive agreement in 1879, and between 1891-94 relations between France and Russia intensified which also led here to a defensive pact. As for the other powers, we see that Italy in 1882 showed proximity to the German side, while England coalesced with the Franco-Russian side.
The fuse ignited on June 28, 1914 with the murder of Francesco Ferdinando, but war broke out only one month after on July 28, 1914 with the declaration of war, so the First World War began.