When Germany unified as one country they were determined to show their strength and try to prove themselves as a great power in Europe.
To prove themselves they attacked France, won and gained the land of Alsace-Lorraine.
Others think it was one or a combination of all three (four including Imperialism) other reasons; Militarism, Nationalism and the formation of the Alliance systems between major countries.
It can be argued that all of these played a major part in the break out of war in 1914; however you must consider that the war may not have broken out without the trigger.
Most people believe the shooting of Franz Ferdinand is the trigger that shot the world into war.
Imperialism during the 19th century and into the early 20th century was viewed as one of the major long term causes of the First World War.The trigger of the war, the shooting of the Archduke Franz Ferdinand could have been viewed as a direct result of nationalism.Nationalism was especially high in Austria-Hungary. Inside Austria-Hungary there were up to 11 different nationalities.Ironically, this worried Germany as if it meant that France and Russia had an alliance it meant that she could be attacked from both sides.However, Britain had no allies within the Great powers, and therefore, she was isolated.The other Great powers became increasingly worried about the strength of the Triple Alliance.Therefore, France and Russia agreed to help each other if any country from the Triple Alliance attacked them, and they signed the Franco-Russian Alliance.Many historians have conflicting views about what caused war to break out in 1914, and many believe there is not one cause to blame but was the result of many conflicts and disputes between different countries over a long period.There are also other causes for the outbreak of World War One including Political systems and developments, Colonial Conflicts and rivalries, The Moroccan Crises, The Balkan Wars and the July Crisis.Alliances and Ententes Were to Blame for the Outbreak of World War One (WWI) In August 1914, World War One broke out.The main cause of the war has never been established and has been among the many debates among historians studying this period.