Tom Clancy's Rainbow Six started in 1998 and as of 2024 consists of 13 entries with 6 expansion pack from early installments.
Formed in 1999 by the world's military, law enforcement, and intelligence agencies to combat the post-Cold War global rise in terrorism, Rainbow is a rapid reaction force consisting of "operators" from nations and organizations worldwide, ranging from special forces soldiers and police tactical unit members to intelligence officers and field experts, trained and equipped to be the most capable counterterrorist professionals in the world, able to handle any terrorist attack, hostage rescue, or takedown that local authorities cannot conduct in an effective, reliable, or timely manner.
Due to the sensitive nature of their operations, such as being deployed in multinational incidents or against threats possessing weapons of mass destruction, and to simply prevent terrorists from knowing of their existence, Rainbow operates in complete secrecy, with only the most senior government, military, and intelligence officials knowing they even exist.
[2] The first Six was former U.S. Navy SEAL and CIA operations officer John Clark, who led the organization from its founding until his retirement.
[b] Though the Rainbow Six universe is generally grounded in reality and maintains its basic premise, recent installments and plot events partially depart from the series' established setting or Rainbow's traditional policies, with Rainbow hosting a publicly visible tactical competition,[b] recruiting non-government or independent operators such as private military company "Nighthaven",[b] and being deployed to defeat invading extraterrestrials.