A major war in Europe had been brewing in the years leading up to it. Alliances were being made and countries were protecting other countries from foreign and internal threats. After Archduke Franz Ferdinand was assassinated by the Black Hand’s Gavrilo Princip, Europe’s move toward war rapidly sped up.
The war was very slow moving. Either side could strike a finishing blow at any point up until the end of the war. New tactics and weapons, which included gas attacks, flamethrowers, and tanks, were introduced over the course of the war.
The United States remained neutral until the final two years of the war. In April 1917, the United States declared war on Germany but did not get into battle until 1918. War was only declared on Germany in this war and none of its allies.
After the war, the countries on the winning side of the war met in France for the peace conference beginning in January 1919. Germany, the Austro-Hungarian Empire, and Turkey were not allowed to attend because the rest of the nations at the conference saw them as the reason for the war. Russia was also not invited to the conference because they dropped out of the war for their revolution which ended in a new Communist government.
The peace conference ended in January 1920. It ended with a new League of Nations which proved to be ineffective; it did not prevent another world war from occuring. The conference broke up each of the losing nations lands and formed new countries or gave bits of their land to existing nations. Even nations on the winning side of the war were not happy with their gains that came from the conference because secret treaties made under the table during the war. This happened most notably to the Italians who were promised a great deal of land but only walked away with the Italian speaking part of the former Austro-Hungarian Empire.