Reunited Kingdom
The Reunited Kingdom refers to the coalition of nations and the restored alliance of Knights Radiant assembled to oppose Odium during the renewed war on Roshar in Brandon Sanderson's The Stormlight Archive. It represents an attempt to recreate the unity that bound the peoples of Roshar in ancient times, before the Desolations scattered them.
Background
In the deep past, Roshar was defended by a unified order of Knights Radiant drawing the nations together against the Desolations of Odium. After the Recreance, when the Radiants abandoned their oaths, that unity collapsed, and Roshar fragmented into many rival kingdoms. By the time Odium's power returned with the Everstorm, the human nations were divided and unprepared.
Formation
Recognizing that no single nation could withstand Odium, Dalinar Kholin worked to forge a new coalition, drawing together kingdoms such as Alethkar, Azir, Thaylenah, and others, bound by treaty and by the reactivated Oathgate network centered on the tower-city of Urithiru. This coalition, sometimes framed as a reunited kingdom of Roshar, served as the political and military structure for resisting Odium's renewed assault.
Significance
The effort to build and hold this coalition together, against mutual suspicion, competing interests, and Odium's manipulations, is a central thread of The Stormlight Archive. The success or failure of this reunification carries the fate of Roshar, and the contest of champions that decides the war hinges on whether the nations can stand together as one.