The war was initiated following the withdrawal of Japanese troops from the Han archipelago after being repelled by the two main guerrilla movements, the Grand National Party in the north and the Han Worker's Party in the south, and the hastily done Hanyang Declaration. With Sierra recognising only the social conservative, nationalist Grand National Party as the rightful heir of Hani, the southern communists were enraged and chose to invade the North, quickly overrunning the central islands and the Bikoru peninsula. At the time, much of the North faced communist insurgencies and sympathised with communist ideals. Within a year, Hanyang was captured and the North was restricted to the northern half of Lusong.