The Causes of World War I

The four MAIN causes of World War I were:

Militarism: Many European countries practiced militarism, which meant that they were all building and maintaining the strongest possible militaries.

Alliances: Agreements between countries, usually a mutual-defense treaty. Austria-Hungary declares war on Serbia. Russia, allied with Serbia, moves in to defend it. Germany, allied with Austria-Hungary, declares war on Russia, and then France too. Britain, allied with France, declares war on Germany. Finally, Austria-Hungary declares war on Russia, which causes  France and Britain to declare war on Austria-Hungary. The Ottoman Empire and Bulgaria then form alliances with Germany and Austria-Hungary. So, World War I begins as Russia, Serbia, France, and Great Britain against Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria.

Imperialism: The practice of a larger country invading and taking over a smaller countryAustria-Hungary takes over several weak Balkans countries. Then, a Serbian assassinates the heir of Austria-Hungary in Bosnia (causing World War I), a country A-H had subjugated as part of it's imperialistic approach. Wanting to take over Serbia, A-H declares war on Serbia and then the tangle of alliances ensues. Eventually, the Ottoman Empire and Bulgaria join the war in order to win land.

Nationalism: Pride in one's nation or race, patriotism. The only reason Russia helped Serbia (and eventually brought Britain, France, and Germany into the war) was because both countries shared a strong Slavic heritage. Nationalism was also the reason why Gavrilo Princep killed Franz Ferdinand

The spark that started World War I was the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, in Bosnia by a Serbian nationalist named Gavrilo Princep. Austria-Hungary then used this as an excuse to declare war on Serbia, setting off a chain reaction of alliances and agreements.

1. Unrestricted Submarine Warfare, February 1915: Germany's announcement that they would use their submarines to sink any ship found in British waters, with no warning.

2. Lusitania, May 1915: British passenger ship, sunk by a German U-boat as part of Germany's announced "unrestricted submarine warfare." 1,198 people died, including 128 Americans. Made more Americans want to enter World War I.

3. Sussex Pledge, May 1916: In response to Germany nearly sinking another passenger ship, the Sussex, America told Germany that it would either stop it's unrestricted submarine warfare, or face retribution. Fearing a strong, fresh enemy, Germany signed the Sussex pledge in which it promised to only sink ships carrying contraband (like weapons for the French), and would help the crew and passengers to a save location before doing so.

4. Zimmerman Note, January 1917: Telegram from German Foreign Minister Arthur Zimmerman to the German foreign minister in Mexico. It promised sections of the United States' land to Mexico if they joined the Germans. If the United States became a problem, Germany would send troops to Mexico and the two countries would do a joint invasion. This telegram was intercepted and decoded by British officers, who gave it to the United States. The Zimmerman Note was arguably the main reason why the United States joined World War I.