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The assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist in Sarajevo set off a chain of events leading to the outbreak of World War I. -
Fought from July 1 to November 18, 1916, the Battle of the Somme was one of the bloodiest battles in history. It aimed to break the stalemate of trench warfare but resulted in over a million casualties. -
Germany invaded Belgium to outflank French defenses. This invasion brought the United Kingdom into the war against Germany, honoring its treaty with Belgium. -
The Gallipoli Campaign, from April 25, 1915, to January 9, 1916, was an Allied attempt to control the sea route from Europe to Russia. The campaign ended in a costly failure with heavy casualties. -
the British ocean liner Lusitania was sunk by a German U-boat, killing 1,198 passengers. This event turned public opinion against Germany and influenced the United States' eventual entry into the war. -
Austria-Hungary declared war on Serbia, starting the conflict that would expand as other nations were drawn in due to alliances. -
The Russian Revolution in 1917 led to the abdication of Tsar Nicholas II and the rise of the Bolsheviks. Russia exited the war following the Treaty of Brest-Litovsk, which allowed Germany to concentrate on the Western Front. -
the First Battle of the Marne was a critical Allied victory that halted the German advance into France. It marked the beginning of trench warfare on the Western Front. -
an unofficial ceasefire occurred along the Western Front. Soldiers from both sides fraternized, exchanged gifts, and played football, reflecting the shared humanity amid the conflict. -
The Second Battle of the Marne, fought in July-August 1918, was a turning point in the war. The Allies, with American support, successfully countered a German offensive, leading to a series of Allied victories. -
The Battle of Verdun, from February to December 1916, was one of the longest and costliest battles in World War I. French forces defended against a massive German offensive, symbolizing French resilience. -
In January 1917, the British intercepted the Zimmermann Telegram, in which Germany proposed a military alliance with Mexico against the United States. The revelation fueled U.S. support for entering the war. -
On April 6, 1917, the United States declared war on Germany, joining the Allies. U.S. involvement provided crucial reinforcements and resources that helped tip the balance in favor of the Allies. -
On November 11, 1918, an armistice was signed between the Allies and Germany, ending the fighting on the Western Front. The armistice marked the end of World War I and led to peace negotiations. -
Signed on June 28, 1919, the Treaty of Versailles officially ended World War I. The treaty imposed heavy reparations and territorial losses on Germany, laying the groundwork for future conflicts.