The significant conflict that sparked the beginning of the 20th century was World War I, which began in 1914. The assassination of Archduke Franz Ferdinand served as the catalyst for a series of political disagreements, alliances, and mobilizations across Europe. It united multiple nations into two major opposing alliances: the Allies and the Central Powers. This war involved unprecedented levels of destruction with trench warfare, new technologies, and massive loss of life, fundamentally altering power dynamics and political boundaries in Europe. Its consequences, including the Treaty of Versailles, paved the way for geopolitical tensions leading up to World War II.