Tom Clancy's Rainbow Six: Rogue Spear is a 1999 tactical first-person shooter video game developed and published by Red Storm Entertainment for Microsoft Windows, with later ports for the Dreamcast, Mac OS, PlayStation, and Game Boy Advance. The sequel to 1998's Tom Clancy's Rainbow Six, it is the second installment in the Rainbow Six series and the last to be published by Red Storm before its acquisition by Ubi Soft in 2000. The game's plot follows the secret international counterterrorist organization Rainbow as they investigate nuclear terrorism in Eastern Europe. Rogue Spear was released on August 31, 1999 to generally positive reviews on PC, but mixed reviews for all other platforms. Critics praised its significant improvements on the original Rainbow Six's formula but criticized the AI behavior which - while improved - acted inconsistently, and the cluttered planning stage that was more burdensome with Rogue Spear's larger and more complex levels. The game sold over 200,000 copies in its first year of release, with almost 500,000 copies sold by 2006. It was nominated for numerous accolades and has been considered one of the best action games of 1999. A PlayStation 2 port was announced, but was ultimately canceled. Three expansion packs for the game were released between 2000 and 2001, adding new missions, weapons, characters, and assorted materials. Two spin-off games—Tom Clancy's Rainbow Six: Lone Wolf, a PlayStation exclusive; and Tom Clancy's Rainbow Six: Take-Down – Missions in Korea, using Rogue Spear's engine—were released in 2002 and 2003 respectively. A sequel, Tom Clancy's Rainbow Six 3: Raven Shield, was released in 2003. In 2006, the United States Department of Defense licensed Rogue Spear's engine for use in training simulation programs.