Tom Clancy's Rainbow Six Siege (often shortened to Rainbow Six Siege) is an online tactical shooter video game developed by Ubisoft Montreal and published by Ubisoft. It was released worldwide for Microsoft Windows, PlayStation 4, and Xbox One on December 1, 2015. The game puts heavy emphasis on environmental destruction and cooperation between players. Each player assumes control of an attacker or a defender in different gameplay modes such as rescuing a hostage, defusing a bomb, and taking control of a capture point. 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.