Tom Clancy's Rainbow Six Siege is a tactical shooter video game developed by Ubisoft Montreal and published by Ubisoft. It was released worldwide on December 1, 2015, for Microsoft Windows, PlayStation 4 and Xbox One. The game puts heavy emphasis on environmental destruction and cooperation between players. Players assume control of an attacker or a defender in different gameplay modes such as hostage rescuing and bomb defusing. The title has no campaign, but features a series of short missions that can be played solo. These missions have a loose narrative, focusing on recruits going through training to prepare them for future encounters with the White Masks, a terrorist group that threatens the safety of the world. It is the eleventh entry in the Tom Clancy's Rainbow Six series and the successor to Tom Clancy's Rainbow 6: Patriots, a tactical shooter that had a larger focus on narrative. However, Patriots was eventually cancelled due to its technical shortcomings, and the team decided to reboot the franchise. The team evaluated the core of the Rainbow Six franchise and believed that letting players impersonate the top counter-terrorist operatives around the world suited the game most. To create authentic siege situations, the team consulted actual counter-terrorism units, and looked at real-life examples of sieges. Powered by AnvilNext 2.0, the game also utilizes Ubisoft's RealBlast technology to create destructible environments.