Fallout: New Vegas is an action role-playing video game, the fourth major installment in the Fallout video game series. The game was developed by Obsidian Entertainment and published by Bethesda Softworks. It was announced in April 2009, and released for Microsoft Windows, PlayStation 3 and Xbox 360 on October 19, 2010. The game is set in a post-apocalyptic open world environment that encompasses a region consisting of parts of Nevada, California, and Arizona. It is set in a world that deviated onto an alternate timeline thanks to atomic age technology, which eventually led to its devastation by a nuclear apocalypse in the year 2077 in an event referred to as "The Great War". This war was caused by a major international conflict between the United States and China over natural resources. The main story of Fallout: New Vegas takes place in the year 2281, four years after the events of Fallout 3. It is not a direct sequel, but it does mark the return of some elements found in the Black Isle Studios-developed Fallout 2. Inon Zur composed its music.