2.1. The causes of the war:
The Austro-Hungarian Empire and the Russian Empire competed for control of the Balkans. At the same time, Serbia was angry about the expansion of the Austro-Hungarian Empire into the area.
France wanted to recover the region of Alsace-Lorraine, which it had lost to the German Empire after the Franco-Prussian War. France and Germany also competed for control of Morocco.
Great Britain saw the supremacy of each merchant navy threatened when the German Empire, become an economic power
These disputes created a pre-war atmosphere, and the European powers continued to increase spending on arms. Governments, through the press, influenced public opinion in favour of war, while pacifist movements, such as the Second International and the Catholic Church, failed in their attempts to avoid war. On 28 June, 1914, Archduke Franz Ferdinand, the heir to the Austro-Hungarian Empire, was assassinated in Sarajevo. The Austrian government blamed Serbia for the assassination and sent them an ultimatum, which was ignored. On 28 July 1914, the Austro-Hungarian Empire declared war on Serbia.
Countries supported one side or the other, based on their own interests pre-existing alliances (the Triple Alliance and the Triple entente):
The Central Powers: The Austro-Hungarian Empire, German and Ottoman Empires and Bulgaria. Italy, when war broke out, it promised to remain neutral because the pact it had signed was to defend one of the other countries only in the case of an attack from another country. As the Austro-Hungarian Empire initiated the attack, Italy didn’t feel obliged to participate.
The Allies: Serbia was allied with the Triple Entente. Later, Belgium, Japan, Italy, Romania, the United States, Greece, Portugal, China and various Latin American republics. In 1915, Italy abandoned its neutrality and joined the Allies to recover Trieste and Istria, Italian territories that the Austrian-Hungarian Empire controlled.