The October Revolution (Russian: Октя́брьская револю́ция, tr. Oktyabr'skaya revolyutsiya; IPA: [ɐkˈtʲæbrʲskəjə rʲɪvɐˈlʲʉtsɨjə]), also known as the Great October Socialist Revolution (Russian: Вели́кая Октя́брьская социалисти́ческая револю́ция, tr. Velikaya Oktyabr'skaya sotsialisticheskaya revolyutsiya), Red October, the October Uprising or the Bolshevik Revolution, was a political revolution, mass insurrection and a part of the Russian Revolution of 1917. It took place with an armed insurrection in Petrograd traditionally dated to 25 October 1917 Old Style Julian Calendar (O.S.), which corresponds with 7 November 1917 New Style (N.S.).Gregorian Calendar.
It followed and capitalized on the February Revolution of the same year. The October Revolution in Petrograd overthrew the Russian Provisional Government and gave the power to the local soviets dominated by Bolsheviks. As the revolution was not universally recognized outside of Petrograd there followed the struggles of the Russian Civil War (1917–1923) and the creation of the Soviet Union in 1922.
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 that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.