Austria-Hungary

Russia lost land that was formed into Finland, Lithania, Latvia, Estonia, Poland and some was added to Romania. Austria-Hungary was broken up into four separate countries: Austria, Hungary, Yugoslavia and Czechoslovakia. Germany lost all its colonial possesions, a piece out of the south-east that was added to Czechoslovakia and a strip of land that included the port city Danzig was given to Poland so it wouldn't be totally landlocked. Bulgaria lost all of its border on the Mediterranean.

The Austro-Hungarian Empire broke up into Austria, Hungary, and Czech Republic

Austria-Hungary's future king was assassinated.

Because the economy of tghe USA supported the ENTENTE from 1914 , and the USA entered the war in 1917. Without the American support France and Britain wouldn't be able to win the war, due to the lower manufacturing capacity and weaker real economy of the ENTENTE.

Franz Ferdinand was killed by Gavrilo Princip in 1914, just before the war.

Bosnia-Herzogivina

Gain? Austria lost its empire, Hungary lost 3/4 of its land. The latter one is widely considered to be the biggest loser of the war. The only gain these two had from the war is the end of the Habsburg monarchy, and their independence from a greater empire.

Any empire becomes nervous when another empire is established, especially when the new empire borders its own.

This is doubly true when some components of the new empire were formerly part of the old one.

No, Austria - Hungary allied with Bulgaria (and Germany) in the First World War. It was invaded by the Allies in 1916.

some countries supported Austria-Hungary (like Germany...) and some supported Serbia (like Russia...) and then World War I started...

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In the final weeks of WW1 Austria-Hungary disintegrated altogether. This is what happened to its territory: *The new state of Czechoslovakia (corresonding rough to the present Czech and Slovak republics) was created from its territory. *Part went to the revived nation of Poland. *Substantial parts went to Serbia to create the them new country of Yugoslavia, which in turn has disintegrated in the last 10-15 years. *Romania almost doubled in size at the expense of Austria-Hungary. *Italy gained a few relatively small areas. *The link between Austria and Hungary was broken. Union between Austria and Germany (including even a customs union) was forbidden. Joncey

The Hungarians wanted the sea opening (the marshal of Austria-Hungarian army even called himself the Admiral, in advance, being sure he will get to the sea).

The Bulgarians were threaten by the Hungarians that if they do not attack, all economical and military support will be halved.

The name for the Central Powers (also known as the Triple Alliance) is derived from the location of these countries; all four were located between the Russian Empire (in the east) and France and the United Kingdom (in the west).

Serbia was one of the countries fighting on the Allies side ( which included Russia, Great Britain and France.) Actually, the ww1 started when Austo-Hungary attacked Serbia. Then Russia, France and UK backed up the Serbs.

Russia was the first Allied Nation to mobilize troops against Austria-Hungary for its declaration of war on Serbia.

They used the assassination of Archduke Franz Ferdinand as an excuse to end the conflicts they had been faced with by Serbia in the Balkans (ex Pig Wars, nationalism within Austria-Hungary). They really wanted to go to war with them because they thought that with Germany as an ally, they could easily defeat Serbia and discourage the raging nationalism threatening to tear Austria-Hungary apart (as demonstrated in the 1848 Revolutions and the Budapest Uprisings). But also they wanted to solidify their position as a power now that Germany was unified (1885 or something ... the date slips my mind at the moment) and was becoming a strong power, over powering Austria (seen in the Austro-Prussian War).

The transformation of the Austrian Empire into Austria-Hungary dates from the 'Ausgleich' (usually tranlated as 'Compromise') of 1867.

In 1866 Austria suffered a disastrous defeat at the hands of Prussia and was in effect expelled from Germany. There was a danger that the Hungarians, who had rebelled in 1848-49, might again rise in rebellion against Habsburg rule. (That said, negotiations for some kind of autonomy for Hungary had been in progress before the war of 1866).

This vast empire (the second largest state in Europe - after Russia) disintegrated in 1918.

It was an empire and a monarchy.

They gave Serbia an ultimatum which said that if they didn't stop trying to be independent then they would go to war with them, of course this then led to the assassination of Franz Ferdinand and the start of the first world war.

Serbia

Austria-Hungary was a multi ethnic state which meant that it was made up of people form many different nationalities. This caused problems when Nationalism took hold because all of the different groups of nationalities wanted their independence, they wanted national statehood. This caused turmoil and instability within the Empire.

an act of terrorism

Germany and Austria-Hungary were big nations in the middle of Europe before the First World War; the Turkish Empire was still big in parts of south-eastern Europe up to the First World War, but had been even bigger in that area a century earlier.