I need help! Can someone please tell me how and why World War One started??

On 28 June 1914, Gavrilo Princip, a Bosnian Serb student, killed Archduke Franz Ferdinand, the heir to the Austro-Hungarian throne, in Sarajevo. Princip was a member of Young Bosnia, a group whose aims included the unification of the South Slavs and independence from Austria-Hungary. The assassination in Sarajevo set into motion a series of fast-moving events that escalated into a full-scale war. Austria-Hungary demanded action by Serbia to punish those responsible. Austria-Hungary declared war on Serbia, when it deemed it had failed to comply. Major European powers were at war within a matter of weeks because of overlapping agreements for collective defense and the complex nature of international alliances. Though the assassination was the event that started the war, it was the last in a long succession of complex causes and events that pitted the nations of Europe against each other.

Archduke Franz Ferdinand (a Serb) was assassinated when he went to Bosnia by the Black Hand group (he was the heir to the Serb throne). Serbia was allied with Austria - Hungary so when he was assassinated war broke out between Bosnia and A-H. Russia supported Bosnia and Germany supported A-H, so when Bosnia refused to arrest the assassins A-H declared war on them. Therefore Germany and Russia were also drawn into the war. Because of the Triple Entente and the triple alliance France and Britain were drawn into the war (britain declared war when germany invaded belgium). hope this helps a bit!

someone cheating in history classes?

well basically:

There were four major causes of World War 1

1) The rise of nationalism, (2) a build-up of military might, (3) competition for colonies, and (4) a system of military alliances.

(1) Nationalism is the belief that loyalty to a nation and its political and economic goals comes before any other public loyalty.

(2) Nationalism encouraged public support for military build-ups and for a country’s use of force to achieve its goals.

(3) During the late 1800’s and early 1900’s, European nations competed to have colonies in Africa and Asia. Competition for colonies strained relations among European countries. Which led to several clashes between certain European countries.

(4) The Triple Alliance also known as the Three Emperors’ League was formed in 1881. Germany’s prime minister, Chancellor Otto von Bismarck, formed a series of alliances to strengthen his country’s security by making Germany an ally of Austria-Hungary and of Italy.

All of these events led up to the assassination of Archduke Frances Ferdinand, heir to the throne of Austria-Hungary, which triggered World War I.

check these websites. They have good information

http://www.firstworldwar.com/origins/causes.htm

http://wiki.answers.com/Q/When_did_World_War_1_sta...

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http://home.att.net/~starfurry/worldwarone.html

http://en.wikipedia.org/wiki/Causes_of_World_War_I

http://history-world.org/world_war_one.htm