Cold war

The conclusion of the Galactic Civil War in 5 ABY marked the beginning of a cold war between the New Republic and a remnant of the Galactic Empire. In addition to a provisional government on Coruscant, the Empire was survived by several remnants in spite of the Galactic Concordance and the dissolution of the Imperial government. One of the remnant factions consisted of political hardliners who opposed the Republic during the cold war, before eventually retreating to the Unknown Regions of space where the First Order was ultimately formed.

Behind the scenes
The cold war was first mentioned in the 2015 reference book Star Wars: The Force Awakens: The Visual Dictionary.