Forefather War

The Forefather War, otherwise known as the Forefather Invasion of the Galaxy, the Alliance War, the Great Selath or the War of Galactic Resistance was a major conflict within the Milky Way Galaxy, with the combined forces of the major governments in the known galaxy resisting the invasion of the S'southi under the Forefathers.

Background
Prior to the Forefather War, several attempts were made by the Ministry of Intergalactic Affairs, a branch of the Lights of Purity, to contact a number of supposed Forerunners living within the Andromeda galaxy. The combined efforts of the Ministry of Divine Knowledge and the Ministry of Intergalactic Affairs lead to the mounting of the Void Journey, in which a Forerunner deep-space exploration vessel from Propriety was used in an attempt to directly contact the Forerunners. Upon the arrival of the vessel, the Forefathers exited their centuries of hibernation and amassed a S'southi army.

Opening Engagements (February-April 2560)
The S'southi Armada, using highly advanced organic-based slipspace technology, arrived at the edge of the Milky Way Galaxy in weeks. As Humanity and the Krythenans were embroiled in their own conflict, the S'southi saw fit to neutralise the largest threat, and attacked the Lights of Purity and various other Remnant factions, which where taken by surprise and suffered massive losses in the opening weeks of the invasion.

As soon as news of the invasion reached Humanity and the Krythenans, both states ended their hostilities and formed the Galactic Alliance in order to counter the S'southi. Membership of the Galactic Alliance only grew as the S'southi got deeper into Covenant and Krythenan space. The S'southi fleet abandoned their attacks on the Lights of Purity and launched an attack on the Krythenan Empire, where they were countered and decisively defeated at the Battle of Matun'ds.

Following the destruction of the initial S'southi invasion, the threat had seemingly passed, though the Galaxy remained on high alert as they dealt with guerrilla stragglers in Krythenan space. The main invasion would begin with the arrival of the S'southi Armada in early May.