There were a number of catalysts, political realities, nation-state alliances, and series of cause and effect events that resulted in the enormous size, scope, and scale of World War I . Decades of historical context is important to understand when looking at how so many countries became involved in fighting...
There were a number of catalysts, political realities, nation-state alliances, and series of cause and effect events that resulted in the enormous size, scope, and scale of World War I. Decades of historical context is important to understand when looking at how so many countries became involved in fighting in World War I. Since the year 1871, Germany had been growing in power and influence in Central Europe.
As the emerging nation-state began forming strategic alliances with Austria-Hungary and Italy, many Western European nations, as well as Russia, became concerned with Germany's growing consolidation of power and political alliances. As such, France and Russia entered into political alliance, and while France and Britain were consistently on the verge of aggression, the two nations entered in a political agreement to protect themselves from the growing power of the German bloc.
By 1904, these political alliances between countries were firmly in place. In the midst of these ever-increasing brewing tensions in Central- and Western Europe, South-Eastern European countries were also experiencing political upheaval and chaos, particularly as the Serbian state became more and more powerful. Austria-Hungary was particularly threatened by the rising power of the Serbian state, considering its similar political and military goals of consolidating power within the boundaries of central/south-eastern Europe.
On June 28th, 1914, when the archduke of Austria was assassinated by a young Bosnian-Serbian man, Austria-Hungary immediately moved to crush the rise of the Serbian state. Germany saw a chance to continue consolidating power by backing Austria-Hungary and encouraged a war against Serbia. This move was a particularly important catalyst for events that followed as countries allied against the rise of Germany in Central Europe began preparing to resist German military involvement in the conflict between Serbia and Austria-Hungary.
Russia, in particular, became quickly involved in the war as it moved to protect its Serbian ally. The French knew they would be attacked by Germany and, as such, also began immediate preparations along with its Russian ally. Britain attempted to stay out of the war preparations, but as the German state made it clear it would seize power over waterways that would threaten British security, the British state also began preparing for war by late July of 1914.
When Germany invaded the neutral state of Belgium on August 2nd, Britain demanded that Germany withdraw its troops, and when this demand was not met, Britain declared war on August 4th, 1914. In 1917, after almost 3 years of attempting neutrality, the United States entered into the war alongside the Allied powers after German submarines continued to attack non-combatant ships as well as attempted to make political alliance with Mexico.