The Temporal Cold War was a conflict fought between several time traveling factions, each from different points in time, and each attempting to manipulate history for its own benefit, in violation of the Temporal Accords. Each of these factions opposed one another in their attempts to gain dominance over the timestream, and often used proxy powers to carry out their missions. They were opposed by a group of temporal agents from the 31st century, who attempted to protect the integrity of the timeline.
Starfleet first became aware of the Temporal Cold War in April of 2151, when a Klingon courier named Klaang crashed in Broken Bow, Oklahoma. Spurred by a desire for Humanity to display an ability to manage its own affairs, Enterprise captain Jonathan Archer elected to push up the launch of Enterprise by three weeks in order to return Klaang to his people. During the course of this mission, Enterprise's crew encountered a group of Suliban on Rigel X, who were actively opposing the Suliban Cabal, a group which was taking orders from a faction in the 28th century. Through Sarin, one of the leaders of the resistance group, Archer learned of the Temporal Cold War and of the Cabal's attempts to destabilize the Klingon Empire. When Enterprise returned Klaang to Qo'noS, the Klingon High Council was made aware that the Cabal had been staging attacks within the Empire, trying to make it appear as if one house were attacking another.