The war was propagated by two major alliances. The Entente Powers initially consisted of France, the United Kingdom, Russia and their associated empires and dependencies. Numerous other states joined these allies, most notably Italy in April, 1915, and the United States in April, 1917. The Central Powers, so named because of their central location on the European continent, initially consisted of Germany and Austria-Hungary and their associated empires. The Ottoman Empire joined the Central Powers in October, 1914, followed a year later by Bulgaria. By the conclusion of the war, only The Netherlands, Switzerland, Spain and the Scandinavian nations remained officially neutral among the European countries, though many of those provided financial and material support to one side or the other.
The fighting of the war mostly took place along several fronts that broadly encircled the European continent. The Western Front was marked by a system of trenches, breastworks, and fortifications separated by an area known as no man's land.[5] These fortifications stretched 475 miles (more than 600 kilometers) [5] and precipitated a style of fighting known as trench warfare. On the Eastern Front, the vast eastern