2.2The war´s Participants and phases: after the Austro-Hungarian Empire Had declared war on Serbia, other European countries chose sides, based on Their pre-existing alliance and own national interests. As a result, two Alliances emerged which then fought each other fot the next four years. –Participants In the war: *The central powers: the Austro-Hungarian Empire was supported By the German Empire and Bulgaria. *The Allied powers: Serbia was supported by Great Britain, France, and the Russian Empire. Later,, they were joined by Japan, Romania, the United States, Greece and Portugal. –Phases of the war: The first world war can be divided into three main phases.1.Initial German offensives 1914:the German Empire made several Rapid offensives, invading Belgium, which was neutral, as well as the north of France. At the fifhting to prevent Russian advances in the east. 2.Trench warfare and new allies 1915-1917: In 1915, the western front between Germany and the Allies stablised and a Period of trench warfare began. 3.Allied Victories and the armistice 1918: Russia withdrew from the war, but the Allies achieved a number of victories both in the east and the west.