Rainbow Six

Tom Clancy's Rainbow Six/Tom Clancy's Rainbow 6
Genres	Tactical shooter
Developers	Ubisoft Montreal Ubisoft Milan Red Storm Entertainment
Publishers	Ubisoft
Platform of origin	Microsoft Windows
First release	Rainbow Six August 21, 1998
Latest release	Rainbow Six Siege December 1, 2015

Tom Clancy's Rainbow Six is a media franchise created by American author Tom Clancy about a fictional international counter-terrorist unit called "Rainbow." The franchise began with Clancy's novel Rainbow Six, which was adapted into a successful series of tactical first-person shooter video games.

Rainbow Six describes Rainbow as an international counter-terrorism operation hosted by NATO and funded by money funneled through the U.S. Department of the Interior.

The base of operations for Rainbow is located in Hereford, England (at the time, home to the SAS), due to the United Kingdom being one of the most accessible countries in the world and having one of the world's foremost special forces units. Most of the characters in Rainbow are American or British, though the NATO countries of France, Germany, Italy, Spain, Canada, and the NATO ally of Israel have at least one representative each.

Clancy describes the structure of Rainbow as having one Director, who oversees the entire operation, and one Deputy Director, who is second in command. Rainbow is portrayed as the "blacker than black" operations, and it works off of its very own intelligence service which has intelligence contacts all over the world. In the book, when Rainbow is called upon for help from another country's government to deal with a terrorist situation, usually only one of the two teams will be sent, but in some situations both will be sent. Both teams have an officer (O-4 or equivalent) as team leader and a senior NCO (E-9 or equivalent) as second in command. Not including the team leader, each team is made up of ten men. Rainbow also has a standard-issue weapons kit. Each team has two snipers.

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Wikipedia