The causes of World War One
World War I, military conflict, from 1914 to 1918, that began as a local European war between Austria-Hungary and Serbia on July 28, 1914; was transformed into a general European struggle by Germany's declaration of war against Russia on August 1, 1914; and eventually became a global war involving 32 nations. Twenty-eight of these nations, known as the Allies and the Associated Powers, and including Great Britain, France, Russia, Italy, and the United States, opposed the coalition known as the Central Powers, consisting of Germany, Austria-Hungary, Turkey, and Bulgaria. The immediate cause of the war between Austria-Hungary and Serbia was the assassination on June 28, 1914, at Sarajevo in Bosnia (then part of the Austro-Hungarian Empire; now in Bosnia and Herzegovina), of Archduke Francis Ferdinand, heir-presumptive to the Austrian and Hungarian thrones, by Gavrilo Princip, a Serb nationalist. The fundamental causes of the conflict, however, were rooted deeply in the European history of the previous century, particularly in the political and economic policies that prevailed on the Continent after 1871, the year that marked the emergence of Germany as a great world power.

II CAUSES OF THE WAR,
The underlying causes of World War I were the spirit of intense nationalism that permeated Europe throughout the 19th and into the 20th century, the political and economic rivalry among the nations, and the establishment and maintenance in Europe after 1871 of large armaments and of two hostile military alliances.
A Nationalism
The French Revolution and the Napoleonic Wars had spread throughout most of Europe the idea of political democracy, with the resulting idea that people of the same ethnic origin, language, and political ideals had the right to independent states. The principle of national self-determination, however, was largely ignored by the dynastic and reactionary forces that dominated in the settlement of European affairs at the Congress of Vienna in 1815. Several peoples who desired national autonomy were made subject to local dynasts or to other nations. Notable examples were the German people, whom the Congress of Vienna left divided into numerous duchies, principalities, and kingdoms; Italy, also left divided into many parts, some of which were under foreign control; and the Flemish- and French-speaking Belgians of the Austrian Netherlands, whom the congress placed under Dutch rule. Revolutions and strong nationalistic movements during the 19th century succeeded in nullifying much of the reactionary and anti-nationalist work of the congress. Belgium won its independence from the Netherlands in 1830, the unification of Italy was accomplished in 1861, and that of Germany in 1871. At the close of the century, however, the problem of nationalism was still unresolved in other areas of Europe, resulting in tensions both within the regions involved and between various European nations. One particularly prominent nationalistic movement, Pan-Slavism, figured heavily in the events preceding the war.

B Imperialism
The spirit of nationalism was also manifest in economic conflict. The Industrial Revolution, which took place in Great Britain at the end of the 18th century, followed in France in the early 19th century, and then in Germany after 1870, caused an immense increase in the manufactures of each country and a consequent need for foreign markets. The principal field for the European policies of economic expansion was Africa, and on that continent colonial interests frequently clashed. Several times between 1898 and 1914 the economic rivalry in Africa between France and Great Britain, and between Germany on one side and France and Great Britain on the other, almost precipitated a European war.

C Military Expansion
a result of such tensions, between 1871 and 1914 the nations of Europe adopted domestic measures and foreign policies that in turn steadily increased the danger of war. Convinced that their interests were threatened, they maintained large standing armies, which they constantly replenished and augmented by peacetime conscription. At the same time, they increased the size of their navies. The naval expansion was intensely competitive. Great Britain, influenced by the expansion of the German navy begun in 1900 and by the events of the Russo-Japanese War, developed its fleet under the direction of Admiral Sir John Fisher. The war between Russia and Japan had proved the efficacy of long-range naval guns, and the British accordingly developed the widely copied dreadnought battleship, notable for its heavy armament. Developments in other areas of military technology and organization led to the dominance of general staffs with precisely formulated plans for mobilization and attack, often in programmes that could not be reversed once begun.

Statesmen everywhere realized that the tremendous and ever-growing expenditures for armament would in time lead either to national bankruptcy or to war, and they made several efforts for worldwide disarmament, notably at the Hague Conferences of 1899 and 1907. International rivalry was, however, too far advanced to permit any progress towards disarmament at these conferences.

The European nations not only armed themselves for purposes of "self-defence", but also, in order not to find themselves standing alone if war did break out, sought alliances with other powers. The result was a phenomenon that in itself greatly increased the chances for generalized war: the grouping of the great European powers into two hostile military alliances, the Triple Alliance of Germany, Austria-Hungary, and Italy and the Triple Entente of Great Britain, France, and Russia. Shifts within these alliances added to the building sense of crisis.

D 1905-1914: Crises Foreshadowing the War
ith Europe divided into two hostile camps, any disturbance of the existing political or military situation in Europe, Africa, or elsewhere provoked an international incident. Between 1905 and 1914 several international crises and two local wars occurred, all of which threatened to bring about a general European War. The first crisis occurred over Morocco, where Germany intervened in 1905-1906 to support Moroccan independence against French encroachment. France threatened war against Germany, but the crisis was finally settled by an international conference at Algeciras, Spain, in 1906. Another crisis took place in the Balkans in 1908 over the annexation by Austria-Hungary of Bosnia and Herzegovina. Because one form of pan-Slavism was a Pan-Serbian or Greater Serbia movement in Serbia, which had as one of its objects the acquisition by Serbia of the southern part of Bosnia, the Serbs threatened war against Austria. War was avoided only because Serbia could not fight without Russian support, and Russia at the time was unprepared for war. A third crisis, again in Morocco, occurred in 1911 when the German government sent a warship to Agadir in protest against French efforts to secure supremacy in Morocco. After threats of war on both sides, the matter was settled by a colonial compromise between France and Germany in November 1911. Taking advantage of the preoccupation of the Great Powers with the Moroccan question, Italy declared war on Turkey in 1911, hoping to annex the Tripoli region of northern Africa. Because Germany's policy of Drang nach Osten ("drive towards the East") obliged it to cultivate friendship with Turkey, the Italian attack had the effect of weakening the Triple Alliance and encouraging its enemies. The Balkan Wars of 1912-1913 resulted in an increased desire on the part of Serbia to obtain the parts of Austria-Hungary inhabited by Slavic peoples, strengthened Austro-Hungarian suspicion of Serbia, and left Bulgaria and Turkey, both defeated in the wars, with a desire for revenge. Germany, disappointed because Turkey had been deprived of its European territory by the Balkan Wars, increased the size of its army. France responded by increasing peacetime military service from two to three years. Following the example of these nations, all the others of Europe in 1913 and 1914 spent huge sums for military preparneSS

III MILITARY OPERATIONS
a Europe thus heavily armed and torn by national rivalries, the assassination of the Austrian archduke had a catastrophic effect.

A Diplomatic Moves The Austro-Hungarian government, considering the assassination the work of the Greater Serbian movement, concluded that the movement must be suppressed by a military expedition into Serbia. Otherwise it might become powerful enough, particularly if aided by similar movements elsewhere, to cause the disruption of the Austro-Hungarian Empire. On July 23 Austria-Hungary sent an ultimatum to Serbia submitting ten specific demands, most of which had to do with the suppression, with Austrian help, of anti-Austrian propaganda in Serbia. Urged by both Great Britain and Russia, Serbia on July 25 accepted all but two of the demands, but Austria declared the Serbian reply to be unsatisfactory. The Russians then attempted to persuade Austria to modify the terms of the ultimatum, declaring that if Austria marched on Serbia, Russia would mobilize against Austria. A proposal, on July 26, by the British foreign secretary, Sir Edward Grey, that a conference of Great Britain, France, Germany, and Italy settle the Austro-Serbian dispute, was rejected by Germany.

B Declarations of War On July 28 Austria declared war against Serbia, either because it felt Russia would not actually fight for Serbia, or because it was prepared to risk a general European conflict in order to put an end to the Greater Serbia movement. Russia responded by partially mobilizing against Austria. Germany warned Russia that continued mobilization would entail war with Germany, and it made Austria agree to discuss with Russia possible modification of the ultimatum to Serbia. Germany insisted, however, that Russia immediately demobilize. Russia declined to do so, and on August 1 Germany declared war on Russia.

The French began to mobilize on the same day; on August 2 German troops traversed Luxembourg and on August 3 Germany declared war on France. On August 2 the German government informed the government of Belgium of its intention to march on France through Belgium in order, as it claimed, to forestall an attack on Germany by French troops marching through Belgium. The Belgian government refused to permit the passage of German troops and called on the signatories of the Treaty of 1839, which guaranteed the neutrality of Belgium in case of a conflict in which Great Britain, France, and Germany were involved, to observe their guarantee. Great Britain, one of the signatories, on August 4 sent an ultimatum to Germany demanding that Belgian neutrality be respected; when Germany refused, Britain declared war on it the same day. Italy remained neutral until May 23, 1915, when, to satisfy its claims against Austria, it broke with the Triple Alliance and declared war on Austria-Hungary. In September 1914 Allied unity was made stronger by the Pact of London, signed by France, Great Britain, and Russia. As the war progressed, other countries, including Turkey, Japan, the United States, and other nations of the western hemisphere, were drawn into the conflict. Japan, which had made an alliance with Great Britain in 1902, declared war on Germany on August 23, 1914. The United States declared war on Germany on April 6, 1917.