The leaders of Austria-Hungary held Serbia responsible for Archduke Francis Ferdinand's death in a terrorist attack in 1914. Austria-Hungary hoped to rally the citizens of their fading empire by going to war against the much smaller Serbia. Austria-Hungary believed a victory would remind their ethnic minorities of the empire's strength, and let other ethnic groups that terrorism would be punished. Wars are expensive, but they can also help an economy. Workers throughout Austria-Hungary would soon be going to work in factories to create weapons and to feed and clothe the soldiers. What Austria-Hungary did not count on was fighting two nations.
Russia has a large Serbian minority and many ties with the Balkan region. Russia was displeased with Austria-Hungary's seizure of Sarajevo, and did not want Austria-Hungary to expand into the Balkan Mountains region. Russia agreed to join Serbia if Austria-Hungary attacked. Austria-Hungary had a military alliance with Germany. An alliance is an agreement to act together. Germany agreed to join Austria-Hungary in its war against Serbia.
Germany and France had been rivals for many years. Germany defeated France in a small war in 1870, and claimed land along the French border. The French people were filled with nationalism and hoped to relive the glory days of Napoleon. France had an alliance with Russia, so the French prepared to join the conflict.
Austria-Hungary declared war on Serbia on July 28, 1914. Russia, Germany, and France joined the fighting within a week. Belgium hoped to remain out of the conflict, but when German soldiers marched across their nation to reach France, the Belgians called on an alliance with Great Britain to help resist the Germans. Like a snowball rolling downhill, European alliances entangled most of the continent into what became known as "the Great War."
The civil ensign of the Austro-Hungarian Empire
The Serbian flag during World War I
The national flag of France
Russian flag during World War I
The flag of the German Empire
The Union Jack of Great Britain