Since most of the governments opened up their archives in 1919 and unclosed an incredible amount of material on pre-war historical material, people have been trying to find the cause of the Great War. Many historians, experts and laymen have come up with a huge scope of possible solutions and explanations. However, the question of guilt is a very controversial and sensitive one, and at some point every answer seems unsatisfactory.
The Alliance System certainly played a very important role, but does not solely explain the outbreak of war. It was rather the base for other causes and crises that finally lead to war. However, without Wilhelm II issuing "Weltpolitik", such an alliance system and its consequences would not have existed.
I can therefore say that Kaiser Wilhelm II's Weltpolitik was the main cause of war, which inter alia brought about the fatal build up of an Alliance System and its consequences that led to war.
Leaders have been forging alliances as time immemorial. These agreements of friendship between two or more countries or parties were designed to advance common goals and secure common interests. However, the pre-war alliances did neither bring advancement nor security, but a war that would last 5 years and that would kill and wound almost 30 million people, that is half of the men mobilized.
Otto von Bismarck had realized the danger of alliances and swept any possibility for any country to form a dangerous diplomatic alignment out of the way. By tying Germany to Russia and Austria Hungary, Bismarck enabled Germany to restrain the leaders of the other two countries, and isolated France. He thus rendered a possible French revenge on Germany impossible; and gave Great Britain, who had big colonial interest but little to become involved with continental alliances anyway, no further reason to do so.
However, when Wilhelm II became Kaiser in 1888, he rashly dismissed Bismarck to conduct his own domestic and foreign policies. The Bismarckian diplomatic system and the so carefully maintained balance in Europe collapsed in the following decade. By refusing to renew the Reinsurance treaty with Russia in 1890, Wilhelm II paved the way for the formation of new alliances: Russia drew away from Germany and Germany became more closely associated with Austria-Hungary. France was thus able to settle any differences it had had with Russia and Britain.
As a result of Wilhelm's new political approaches, France and Russia became allies in 1892. The Triple Alliance between Germany, Austria-Hungary and Italy was renewed in June 1902. Only a couple of month later, in November, the Franco-Italian Entente was signed. Germany's Foreign Minister Bernhard von Bülow's claim for "Germany's place in the sun" on December 6, 1897 is known as the official announcement of Weltpolitik, which mainly concentrates on expansion of the colonial empire and the construction of a navy that could rival or, even better, exceed the British one. Wilhelm's decision to pursue Weltpolitik made it impossible for Britain to stay neutral. As a result, Britain and France resolved their colonial tensions and signed the Entente Cordiale in April 1904. Three years later, in 1907 the Anglo-Russian Entente was signed, which along with the Entente Cordiale formed the Triple Entente. And so, the two major war alliances where formed.
It could be argued that the now built Alliance System did not make a war inevitable, since all agreements were rather uncertain: The alliance between Germany and Austria-Hungary was by far the firmest one. It was however uncertain whether or not Germany would back up Austria-Hungary in any of the Balkan affairs. The attitude of the Triple Alliance was extremely ambiguous, and any arrangements within the Triple Entente were very loose, the Entente Cordiale did not even contain a military commitment.
However, there are many points that suggest that the Alliance System did indeed pave the way that led to World War I, inevitably. Firstly, the Alliance System was built on war-footing. This intensified the already existing tensions between the powers, and created an arms race that made a war much more likely. Weltpolitik had been determined to set up a navy that was at least as strong as the British one. Within only four years after the formation of the Triple Entente in 1907, Germany mobilized nine dreadnoughts, after it had ordered 41 of those battleships in 1900. Consequently Britain built twice as many. This started another chain reaction and gave European powers the feeling of having to get ready for war. Everyone felt the need to have the strongest army, the best navy, the most skilful troops. Apart from the arms race this also led to many misjudgements: Germany's flawed "Schlieffen Plan", to invade France via Belgium, was based on the assumption that a war with France would mean a war with Russia.
In addition, the forging of the alliances carried much secretiveness with it and thus caused much suspicion and distrust among the European powers, which made diplomats very judgmental and generally suspicious and contributed too many of the crises preceding the war getting out of hand. The members of the Triple Entente, for example, made various agreements inter alia with Japan, Portugal, Spain and America; and France even concluded a secret agreement with Italy, which made her alliance commitments, namely to help Germany in case of a French attack, worthless.
Another problem was that Germany felt very threatened because of its geographic position. In case of war the powers of the Triple Alliance Germany, Austria-Hungary and Italy, located in the center of Europe and therefore also called the Central Powers, would have to face a battle on two fronts. The German Press even talked about "encirclement" and being surrounded by enemies on all sides. William II reacted with issuing an even more vigorous foreign policy in order to destroy cohesion among the Triple Entente powers, which caused a series of international crises from 1905 to 1914 contributing to the outbreak of war.Â
Lastly, and probably most importantly, the Alliance System brought the crucial problem with it that as soon as there was a conflict between two countries belonging to different alliances, the other powers would be drawn into war. Exactly this happened after the assassination of Franz Ferdinand in Sarajevo in 1914. When Austria-Hungary declared war on Serbia, Russia having a protectorate on Serbia had to come to its aid and declared war on Austria-Hungary. Germany coming to Austria-Hungary's aid was only the start of a large chain reaction that brought the rest of the European powers into war as well, causing the First World War.
In conclusion I can say that the extend to which the Alliance System can be said to be the main cause of war is huge but limited: The Alliance System brought about an arms race and mobilization, it made many powers estimate their power and strength wrongly, and created further mistrust among the alliances. It also made Germany feel particularly threatened about it geographical position and enhanced its decision to go to war. Most importantly though, it brought about chain reaction that brought the European powers one after another into war and thus created the disastrous years of the Great War. However, without Kaiser Wilhelm II's Weltpolitik no such alliance system would have existed. Germany can also be held responsible for the fact that World War I broke out in 1914 and not earlier. The alliances were originally strictly defensive but after the assassination of Franz Ferdinand Germany changed her attitude and guaranteed Austria full support in anything that it might undertake against Serbia. Germany was clearly provoking war in doing so. The theory of Germany seeking aggressively for expansion and war is also supported by the historian Fritz Fischer. In the end, I am of the opinion that Wilhelm II contributed the most to causing World War I.