The main causes of World War I, which began in central Europe in late July 1914, included many factors, such as the conflicts and hostility between the great European powers of the four decades leading up to the war. Militarism, alliances, imperialism, and nationalism played major roles in the conflict as well. The immediate origins of the war, however, lay in the decisions taken by statesmen and generals during the July Crisis of 1914 caused by the assassination of Archduke Franz Ferdinand and his wife Sophie by Gavrilo Princip, an irredentist Serb and member of the Serbian nationalist organization, the Black Hand.
The crisis came after a long and difficult series of diplomatic clashes between the Great Powers over European and colonial issues in the decade before 1914 that had left tensions high. In turn these diplomatic clashes can be traced to changes in the balance of power in Europe since 1867. The more immediate cause for the war was tensions over territory in the Balkans. Austria-Hungary competed with Serbia and Russia for territory and influence in the region and they pulled the rest of the Great Powers into the conflict through their various alliances and treaties.
Some of the most important long term or structural causes were the growth of nationalism across Europe, unresolved territorial disputes, an intricate system of alliances, the perceived breakdown of the balance of power in Europe, convoluted and fragmented governance, the arms races of the previous decades, previous military planning, imperial and colonial rivalry for wealth, power and prestige, and economic and military rivalry in industry and trade – e.g., the Pig War between Austria-Hungary and Serbia. Other causes that came into play during the diplomatic crisis that preceded the war included misperceptions of intent and delays and misunderstandings in diplomatic communications.
The various categories of explanation for World War I correspond to different historians' overall methods....