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Archduke Franz Ferdinand of Austria-Hungary and his wife were assassinated by Gavrilo Princip. This event directly triggered the start of World War I. Austria-Hungary declared war on Serbia soon after. -
Austria-Hungary sent Serbia a harsh ultimatum after the assassination. Serbia's partial rejection led to Austria-Hungary declaring war. This escalated tensions among European powers. -
Germany declared war on Russia in support of Austria-Hungary. This action activated alliances on both sides. It expanded the war across Europe. -
Germany declared war on France to preemptively stop an attack. France was an ally of Russia. This solidified the conflict on the Western Front. -
Germany invaded neutral Belgium as part of the Schlieffen Plan. This angered Britain, which had pledged to protect Belgian neutrality. Britain declared war on Germany the same day. -
German forces defeated Russia in a decisive Eastern Front battle. This stopped Russia's advance into East Prussia. It showcased Germany's strong military strategy early in the war. -
German forces advanced toward Paris but were stopped by Allied troops at the Marne River. This battle marked the end of Germany's quick offensive. Trench warfare began soon after. -
The Allies launched an attack to capture the Dardanelles Strait and weaken the Ottoman Empire. The campaign failed, resulting in heavy Allied losses. It became a significant victory for the Ottomans. -
Italy entered the war on the side of the Allies, leaving its former alliance with Germany and Austria-Hungary. Italy hoped to gain territory. This expanded the war to the Italian Front. -
Germany attacked France at Verdun in one of the longest and bloodiest battles of the war. The French successfully defended Verdun but suffered heavy casualties. This battle symbolized French resistance. -
The Allies launched an offensive against Germany along the Somme River. Over a million soldiers were killed or wounded. It was the first battle to use tanks in warfare. -
Germany sent a secret telegram to Mexico, urging them to join the war against the U.S. in exchange for territory. The message was intercepted and made public, outraging Americans. This helped bring the U.S. into the war. -
The United States declared war on Germany, joining the Allies. American troops and resources gave the Allies a significant advantage. This shifted the war’s momentum. -
The fighting officially stopped when Germany signed the armistice with the Allies. This marked the end of World War I. It set the stage for peace negotiations in Paris. -
The Treaty of Versailles formally ended World War I. It imposed harsh penalties on Germany, including reparations and territorial losses. This treaty aimed to prevent future wars but planted the seeds for future conflict.