World War 1 was fought between the allied and the central powers from 1914 to 1918. It was fought between the central powers consisted of Germany, Austria- Hungary, Turkey and Italy and the allies consisting of U.K , France, Russia and U.S.A. The war in itself is considered a notable example of a total war as all the belligerents used every means of warfare including chemical warfare to try to win.
The war ended with an allied victory after the armistice in 1918. The war was followed by several treaties imposed on Germany and her allies, the most infamous of these being the Treaty of Versailles. The treaty of Versailles contained a very important war guilt clause which stated “The Allied and Associated Governments affirm and Germany accepts the responsibility of Germany and her allies for causing all the loss and damage to which the Allied and Associated Governments and their nationals have been subjected as a consequence of the war imposed upon them by the aggression of Germany and her allies.” the importance of this clause was that it blamed the war solely on Germany. Thus we see how the official primary sources blamed German aggression as the main and only cause of the war.
However the causes of the war are now widely debated by historians with some going as far as blaming U.K. for the war. One such historian is American Paul.W. Schroeder. He says that the cause of the war was what he called Britain's “encirclement" policy which was directed at Austria-Hungary. Schroeder argued that British foreign policy was anti-German and even more anti-Austrian as Britain never took Austria-Hungary seriously. It was British policy to always force concessions on the Dual Monarchy with no regard to the balance of power in Central Europe. Schroeder claimed that world war 1 was thus a "preventive war" by Germany to help maintain Austria as a power, in the face of the crippling British "encirclement policy" which would have otherwise broken-up the state.
Historian Fritz Fischer on the other hand states that the war was caused because of domestic politics in countries like Germany. He says that the Germans deliberately sought a war which would distract the population and whip up patriotic support for the right wing conservative government which was under threat of the powerful emerging left. John Rohl uses German documents to tell us how the Kaiser and the Army leadership wanted to start a war at once in December 1912. The only reason for the delay of the war was due to the objections from Grand Admiral Alfred Von Tirpitz, who supported the idea of starting a war but said that the German Navy needed more time to prepare and asked that the war be put off until the summer of 1914. Fischer also claims that there was a 'will to war' amongst the leaders of Germany and that the German government had a plan of expansion very similar to that of Nazi Germany in the 1930s. thus we how many people still believe Germany to be responsible for starting the war.
Some historians also list the Franco-Prussian War as one of the main causes for the war. The war unified Germany into an empire thus upsetting the balance of power in continental Europe. At the same time it also led to the splendid isolation of Britain and the forced isolation of France by Bismarck. It also began the alliance system between the different powers which changed the war from a regional conflict to a worldwide one. The alliance system was used as an excuse by Britain to join the war as the German Schlieffen Plan which was made to deal with a simultaneous French and Russian attack involved invading Belgium which had an alliance with Britain Thus we see how the Franco -Prussian War set of a chain reaction of events which culminated in the first world war.It is further said that the initial isolation of France by Bismarck and then the popular revanchist movement led to france becoming more hostile towards Germany. Which resulted in them forming an alliance with Russia. This alliance forced the germans to attack them to protect their western front before attacking Russia.. Thus we see how the Franco Prussian War led to the alliance system which led to a regional conflict turning to a world war.
Historian Andreas Hillgruber claims that the war broke out due to a calculated risk by the germans to break the informal Triple Entente of Russia, France and Britain by encouraging Austria-Hungary to invade Serbia and thus provoking a crisis in an area that would concern only St.Petersburg. Hillgruber argued that the Germans hoped that both Paris and London would decide the crisis in the Balkans did not concern them and that lack of Anglo-French support would lead the Russians to reach an understanding with Germany. However this risk went wrong and thus led to the war
Historian Emil Ludwig and Ruth Henig blame “a few dozen incapable leaders” and called the war a result of “failure of statesmanship and hope”. Henig states that “By 1912, most European governments had come to believe that a general European war was inevitable and that the problems which plagued them at home and abroad could no longer be settled by negotiation and diplomacy… In these circumstances, war seemed to offer an attractive way out …” The strongest support for this theory has come from a quote from British Prime Minister (during world war 1) David Lloyd George who accepted this theory and said “We muddled into war”
Historian Samuel R. Williamson however lays the blame of the crisis on mainly the Balkan Wars, he claims that as a result of the defeat and subsequent weakening of Turkey and Bulgaria the balance of power in the Balkans was disrupted. This later led to the tensions between Serbia and Austria. These in turn led to the immediate cause of a war, the assassination of archduke Franz Ferdinand. This assassination of the heir to the Austrio-Hungarian Empire by the agents of a rival nation played a very significant role in lighting the matchbox that was Europe. The assassination led to a conflict between two small powers which was magnified when these two powers used their respective alliances to turn the whole affair from a regional conflict into a world war.
Thus after the evaluation of all the various viewpoints presented by historians it can be concluded that the war was caused mainly as a result of the entangling alliances system and the conflict in the Balkans between Serbia and Austria-Hungary. The two worked hand in hand to start the war. The concept of military alliances that flourished during the Bismarckian era tied the fate of each and every European power together in a web so tight that if one of them fell all of them would fall. The war between Austria-Hungary and Serbia was unavoidable but the progression of the conflict from a regional war avenging an assassinated Archduke to a world wide one was solely because of these the entangling alliance system. Had the alliance system not existed the war would have been another one of the small Balkan wars which had preceded World War 1. Similarly had the conflict in the Balkans not existed, there would have been an alliance system but there would have most likely been no war. The German Chancellor Otto Von Bismarck even said that ““One day the great European War will come out of some damned foolish thing in the Balkans.” -----------------------
 Schroder, Paul "World War I As A Galloping Gertie" pages 142-151 fromThe Outbreak of World War I edited by Holger Herwig, Boston: Hougthon Mifflin, 1997.  Fischer, Fritz Germany's Aims In the First World War, W. W. Norton; 1967  Röhl, John "1914: Delusion or Design" pages 125-130 from The Outbreak of World War I edited by Holger Herwig, Boston: Houghton Mifflin, 1997 page 129  http://www.johndclare.net/causesWWI_Answer1.htm
 Herwig, Holger H. "Andreas Hillgruber: Historian of 'Großmachtpolitik' 1871-1945," pages 186-198 from Central European History Volume, XV 1982 page 190  Williamson, Samuel R. Jr., Austria-Hungary and the Origins of the First World War, 125-140