World War 1 was caused by a series of events triggered by Serbia’s response to Austria-Hungary’s demands, and the treaty alliance system that ensured that many other countries would be drawn into the conflict.
France duly rejected Germany’s ultimatum and began its own mobilisation – though the army was ordered to keep 10km back from the Franco-Belgian border. Germany declared war on France on August 3.
World War Two started in 1939 when Adolf Hitler began taking over countries. World War Two ended in 1945 after the United States dropped two atomic bombs on Hiroshima and Nagasaki, in Japan.
Because all of the other countries involved in WW1 agreed to make Germans pay for all of the costs of WW1. That's part of the reason why WW2 started.
The causes of World War I remain controversial.World War I began in the Balkans in late July 1914 and ended in November 1918, leaving 17 million dead and 20 million wounded.. Scholars looking at the long-term seek to explain why two rival sets of powers – Germany and Austria-Hungary on the one hand, and Russia, France, and Great Britain on the other – had come into conflict by 1914.
World War I began as a clash of 20th-century technology and 19th-century tactics, with the inevitably large ensuing casualties. By the end of 1917, however, the major armies, now numbering millions of men, had modernised and were making use of telephone, wireless communication ,  armoured cars , tanks ,  and aircraft.
World War 1 started when Archduke Franz Ferdinand of Austria was assassinated on June 28, 1914. This was the immediate cause but there were a series of events which triggered the war. See below for more information and facts about how World War 1 started.
World War I began in 1914, after the assassination of Archduke Franz Ferdinand, and lasted until 1918. During the conflict, Germany, Austria-Hungary, Bulgaria and the Ottoman Empire (the Central ...
Thirty-two countries were involved in World War I. The United States, Russia, Italy, Britain and France were the core of the Allied Forces, and they fought against a group of countries known as the Central Powers, which included Austria-Hungary, Bulgaria, Germany and the Ottoman Empire.
Of all the Asian countries involved in World War I in some manner, India, a colony of the British Empire at the time, sent the most: 1.3 million troops and laborers went to the imperial war effort. China was officially neutral but provided about 200,000 laborers to the Allied forces to repair tanks.