Long-term Causes: Militarism
Militarism is the principle/policy of maintaining a large military. The European countries had become divided by a weapons race going on between the larger territories. Between the years of 1870 and 1914 the armies of bother Germany and France had doubled, as well as a large competition occurring between Britain and Germany for control of the seas. The British had begun introducing a ship known as the "Dreadnought," which was a very effective military vessel, in 1906. This led to Germany creating their own form of battleships. Later on as well, a German named Von Schlieffen thought up a plan on how to attack France through Belgium in case of an attack by Russia on Germany.
Alliances
Alliances were agreements between two or more countries to aid each other when needed. An alliance is a form of contract, and once signed, those countries become allies. Between the years of 1879 and 1914 many alliances were created between many countries and territories. This meant that many countries were forced into war if one of their allies was attacked or declared war on another country.
Imperialism
Imperialism is the process in which one country/territory takes over other areas and subjects them to their rule. By 1900, the British Empire had taken control of five continents, while France had control of large portions of Africa. With the Industrial Revolution causing a new rise in Industrialism, countries began to seek new markets of trade with other regions. The land controlled by Britain and France led to increased tensions with Germany, who was still trying to control new areas, but only acquired small areas of Africa.
Nationalism
Nationalism is the feeling of devotion and loyalty to one's country, also known as patriotism. After Napoleon's exile to the island of Elba, the Congress of Vienna met to sort out issues in Europe. The representatives of Britain, Austria, Prussia and Russia decided to divide Germany and Italy in the new Europe being implemented. This lasted til 1861 for Italy, where strong nationalist factors led to the re-unification of the country, while Germany's re-unification came during 1871. The settlement after the Franco-Prussian War left the country of France angry at the loss of one of their territories (Alsace-Lorraine) to Germany, leading to the country to attempt to regain control. Austria-Hungary and Serbia also had large areas in which there were many different groups of nationalists, all of whom wanted to gain their freedom from the states they lived in.
Short-term Causes: The Assassination of Archduke Franz Ferdinand
The assassination of the Archduke took place on June 28, 1914, by the hand of a Serbian nationalist man named Gavrilo Princip. Ferdinand was the heir of the Austro-Hungarian Empire, and was visiting Bosnia and Herzegovina to inspect the imperial forces stationed there. Gravilo did not agree with the archduke's ideas for government, so him and a few others attempted to kill him. The first attempt failed, due to the attacker's bomb hitting not the archduke's vicinity, but instead bouncing off the back of the car he was driven in. This injured several bystanders and an officer. The second and final attempt occurred when the archduke and his wife traveled to visit the injured officer. Their car took a wrong turn, leading them directly into the path of Gravilo Pricip, who took aim with his gun and shot both the archduke and his wife at point-blank range, fatally wounding them.