From 1871 to 1814, European great powers such as France, Germany or England, but also other European countries, did not encounter any major wars. Indeed, the only military action was taking place in the non Western world with wars of conquest in Africa for instance. Nevertheless, this long period of peace was not as stable as it may seem: some tensions rose between countries in Western Europe, creating new alliances, and several crises in the Balkans could have quickly led to a major war.Finaly, on June 28 1914, the assassination of Archduke Francis Ferdinand from Austria and his wife by a terrorist Organization in Sarajevo was the last straw. As Austria declared war to Serbia on July 28, great powers, like Russia that was determined to fight against Germany and Austria but also France, eager to gain back Alsace Lorraine and later England, defending Belgium’s neutrality, joined a war that soon became World War I.Germany’s economical importance intimidated other countries. Indeed, Bismarck, who feared that France and Russia allied against them, signed a defensive alliance with Austria in 1879 and later with Italy named the “Triple Alliance”.Indeed, in North Africa, France had dangerous colonial ambitions for Italy, which therefore made the decision to ally with Germany and Austria. Even though German Bismarck had kept a separate treaty with Russia to improve relations, it was soon canceled because considered incompatible with the Germany-Austria alliance. As expected, France and Russia allied together and German foreign policies made the British to improve relations with France.A Bosnian crisis started in 1908 when Austria decided to annex Bosnia and Herzegovina, even though the two countries were only supposed to be under their protection. Austria had made this dangerous step to stop the possible creation of a large Serbian kingdom including most of the south Slavic speaking territories. While Serbs were outraged, Russia supported them and denounced Austria’s action. While Russia’s main interest was to increase their political power in the Balkans, the Serbs prepared for war against Austria. William II, trying to impose his annexation of Bosnia and Herzegovina, warned Russia that a war against Austria would also mean a war against Germany. The Russians, after being defeated and weakened during the Russo-Japanese War in 1904, preferred to move back. Nevertheless, it is important to note that Russia’s pride at the time could not accept such a humiliation and that it was probable that they would seek revenge later.Crisis continued when Bulgaria, Serbia, Montenegro and Greece allied as a Balkan League to defeat the Turks. Unfortunately, this first Balkan War only led to a disagreement between the victorious countries on how to divide the conquered territories and also a second crisis in 1913. Indeed, Greece, Serbia, Romania and the Ottoman Empire invaded Bulgaria, owner of only a minor part of Macedonia, which increased again tensions between the great powers. Taking the assassination of their Archduke Francis Ferdinand as a reason to use force against Serbia, Austria relied on Germany’s support to put pressure on Serbia. In the mean time, Russia was determined to seek revenge by defending Serbia after being humiliated in 1908 during the Serbian crisis.After a non effective ultimatum to Serbia on July 23 because of very difficult demands, Austria declared war on July 28 while Tsar Nicholas II mobilized an important part of the Russian army to fight against Austria. On July 29, the Russian army was fully mobilized, forcing Germany to declare war on them on August 1. German general Alfred von Schlieffen had organized a two front war plan with France and Russia knowing that the two countries had made an alliance in 1894. England finally declared war on France on august 3 and on august 4, England declared war against Germany because of violating the neutrality of Belgium.Facing a new unified powerful Germany, European countries such as Russia, France and England, were looking for ways to be stronger since tensions appeared. Two alliances, the Triple Alliance (Germany, Italy and Austria) and the Triple Entente (France, England and Russia) clearly separated Europe in two groups made of powerful countries, which led to an even more destructive world war after new series of crises of the Ottoman Empire in the Balkans. Indeed, we could consider these alliances as the long range cause that led to a world war. Crises in the Balkans happened fast and acted as almost immediate triggers of the war, worsening relations between countries.