World War I (WWI), which was predominantly called the World War or The Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe. It began on 28 July 1914 when Austria-Hungary declared war against Serbia and lasted until 11 November 1918 after the German Empire and the Allies signed an armistice.
It caused the deaths of 40 million people (including both soldiers and civilians). The geopolitical changes it generated in most of the world after its eventual outcome were a direct cause for World War II more than 20 years later.
World War I is notable for stalemate trench warfare on the western front, and the development and application of new technology in warfare such as tanks, airplanes and submarines.
