The Triple Alliance was a military alliance between Germany, Austria-Hungary, and Italy that was formed in 1882.

The Triple Entente was a loose alliance between France, Russia, and the United Kingdom that was formed in the early 20th century.

The assassination of Archduke Franz Ferdinand of Austria on June 28, 1914, was the immediate cause of World War I.

The rise of nationalism in Europe in the 19th century led to increased tensions between the European powers and contributed to the outbreak of World War I.

The arms race between the European powers was a competition to build up military forces in the years leading up to World War I.

The desire for colonies and resources was a major factor in the outbreak of World War I, as the European powers competed for control of new territories and resources in Africa, Asia, and the Middle East.

World War I started on July 28, 1914, when Austria-Hungary declared war on Serbia.

World War I ended on November 11, 1918, when an armistice was signed between the Allies and Germany.

An estimated 17 million people died in World War I.

Russia suffered the most casualties in World War I, with an estimated 1.7 million soldiers killed.

Austria-Hungary was the first country to declare war in World War I, when it declared war on Serbia on July 28, 1914.

The United States was the last country to declare war in World War I, when it declared war on Germany on April 6, 1917.

Bulgaria was the first country to surrender in World War I, when it signed an armistice with the Allies on September 29, 1918.

Germany was the last country to surrender in World War I, when it signed an armistice with the Allies on November 11, 1918.

The Treaty of Versailles was a peace treaty that ended World War I and was signed on June 28, 1919.