It is believed and accepted by many that the assassination of Arch-Duke Franz Ferdinand—heir to the Austria-Hungary throne—on 28 June 1914 in Bosnia began the first World War. Austria-Hungary then declared war on Bosnia, and as a result of interconnected treaties, many of the countries were dragged into the conflict. For a summary of how the war started, visit http://www.firstworldwar.com/timeline/1914.htm and http://www.firstworldwar.com/origins/causes.htm

Although the assisination of the Archduke was a cause, it cannot be seen as THE main reason. Too much had happened before that resulted in the war in Europe. For example, the Balklans Crises and Wars provided much of the anger and tension between Austrio Hungary and Russia - Serbia in particular. The incidents involving Germanys foriegn policy of 'Weltpolitik' against the French and the British in incidents such as the morrocan crises, the daily telegraph affair and the extensive naval race were all extremely big factors. All this brought great rivalry between the major powers and were the main reasons for war. All out European War was close at many other times - the assasination was merely a small incident by Serbian terrorists - war was always on cards at that time.

The assassination of Arch Duke Franz Ferdinand was merely the lighting of the fuse on a powderkeg that had been growing for years. Each of the parties in the war were trying to maintain their position with regard to colonies throughout the world, their role as maritime powers, and trying to make themselves the dominant power in that part of the world. You need to look at the Franco-Prussian War as a part of the buildup, along with the rise in power of Bismarck in Germany, the overall problems in Russia (including the Russo-Japanese War after the turn of the century), the Balkans, and other parts of Europe and Asia. Keep in mind that this was largely a family fight, as the leaders of Germany, Russia and England were direct relatives, and the Grand Duke of Austria-Hungary was a relative by marriage. Take a look at Barbara Tuchman's book "The Guns of August" for an explanation of how the powderkeg was lit, and go to Robert Massie's "Dreadnought" for a pretty good explanation of a portion of the buildup of the powderkeg as he tracks the buildup of the Naval Races as each side tried to build bigger, faster and more powerful battleships as a means of showing their power to the world.

Historically, it is seen as the assassination of Arch Duke Ferdinand, the heir to the Austro-Hungarian throne. He was shot in July 1914 by a Serbian terrorist group "The Black Hand". Austria-Hungary declared war on Serbia, which prompted Russia to side with Serbia, France sided with Russia, Germany declared war on France, and invaded through Belgium which caused Britain to declare war on Germany... Very complicated. However, there was huge tension in Europe at that time as the great empires were shifting and changing. It is now known that the Serbain terrorist group was sponsered by Russia. It is probably the case that the assassination was simply the excuse Austria-Hungary was looking for to gain new territory, and they unwittingly caused a cascade of declarations of war, based on tensions between empires and historic alliences, that lead to WW1.

Mobilisation of Russian troops was the biggest cause. Russia was set to achieve 2,000,000 in its standing army by 1917. This threatened Germany and Austria-Hungary's existence and so they were in a race against time to achieve war to have any chance of surviving as great powers. However this only created a world war (including Britain and France) because of the the Triple Alliance set up by Bismark and the Triple Entente set up to counter the Triple Alliance. A combination of the two i believe. Franz Ferdinand is widely accepted, even by the German General of Staff Moltke, as an excuse to provoke a war as soon as possible. Unfortunately for the Central Powers, by this time it was too late.

The sparking incident was the assassination of Archduke Franz Ferdinand in Sarajevo. What turned it into a huge conflict were a system of secret alliances. The German Kaiser had basically given Austria carte blanche to do as she pleased with German protection. Likewise, Edward VII had created an alliance with France that would entangle the UK in any future war on the Continent. +5

The Guns of August by Barbara Tuchman is an excellent referece for a detailed analsis of the beginning of the war.

The assassination of Archduke Francis Ferdinand at Sarajevo,the capital of Austria-Hungary on 28th June 1914 was the immediate cause and just after a month of it on 28th July 1914 is believed to be the start date of WW1.

WW1 had been brewing since 1902. That was the year that Zionism tried to buy Palestine from Turkey but was refused. It was then that the die was cast to take down the Ottoman Empire, allowing the Zionists to obtain it as spoils of war. All they had to do was ignite a war in which Britain would become involved and then apply enough pressure against Britain to pull the United States into the war. Using this tactic, the Balfour Declaration was created, which gave them the rights to Palestine.

The assassination of Arch-Duke Ferdinand.

The assassination of Arch Duke Franz Ferdinand.

There were a number of reasons for WWI but at the bottom of the pile and not widely spoken of was the manipulation of a number of counties by the Rothschild family in their continued effort to control the world's currencies. From what I have last read the Rothschilds own all but three of the currencies in the world. They control and cause wars as well as other situations around the world so they can make more money. It is an octopus with many tenacles. They pull a string and the world jumps.