The Triannon War was a war between religious factions which broke out in the 2050s on the planet Triannon.
The reason for the war was the different religious view of the "Makers". While one faction believed the "Chosen Realm" was created in nine days the other faction believed the creation took ten days. The Triannons of both factions could be differentiated by the red and black tattoos on different sides of their faces.
In November 2153 the leaders of the two factions, Pri'Nam D'Jamat and Ceris, saw the result of this war, the destruction of every city and building on the planet's surface and millions dead. Captain Jonathan Archer of the Earth Starfleet vessel Enterprise NX-01 told D'Jamat that the war was ended in March 2153. (ENT: "Chosen Realm")