This is a brief summary of what was the first great war.
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Europe at the beginning of the twentieth century was made up of alliances, on the one hand THE TRIPLE ALLIANCE made up of GERMANY, AUSTRIA-HUNGARY AND ITALY and THE TRIPLE ENTENTE that made up UNITED KINGDOM, RUSSIA AND FRANCE, that was how they were initially.
These countries belonged to the great powers of the time.
The AUSTRIA-HUNGARY empire, or as AUSTROHUNGARO was known, was run by the EMPEROR OF AUSTRIA AND HUNGARY'S KING FRANCISCO JOSE who by 1914 had 66 years on the throne and who had named as his successor his nephew the ARCHIDUQUE FRANCISCO FERNANDO, He and his wife were murdered during a visit to SARAJEVO, their murderer was a Bosnian student on June 28, 1914, the student had shot the archduke and his wife.
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This made EUROPA convulse and a month later the WAR between the TRIPLE ALLIANCE and the TRIPLE ENTENTE was declared. BELGIUM declares itself neutral.
In this war you will see the difference between the traditional war with its riders on horseback against modern weapons such as the machine gun among others and the implementation of the terrible GAS MOSTAZA.
In 1915 Italy leaves the TRIPLE ALLIANCE and joins the TRIPLE ENTENTE.
In 1917 enters the US war and joins together with JAPAN to the TRIPLE ENTENTE, which made that GERMANY was overcome but continued to resist.
In 1918 RUSSIA retires due to its internal Revolt and GERMANY launches an attack with all but finally they are defeated and they sign the ARMISTICE that puts an end to the war on November 11, 1918.
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The TREATY OF VERSAILLES imposes GERMANY and its allies to pay war reparations and are stripped of parts of their lands, this causes an upset in the GERMAN people that would give rise in about 20 years to the rise of Adolf Hitler and his Third Reich.
BUT THIS IS A THEME OF ANOTHER POST ...