This chapter traces the evolution of the Darul Islam rebellion in West Java to explain how the group shifted from one fighting against colonial forces to one staging an insurgency against the Indonesian Republic that has inspired subsequent generations of Islamist activism. The group turned toward armed resistance against the government to protect its organizational interests and authority in the face of perceived external aggression. During the rebellion, however, Darul Islam was severely weakened by the combination of effective military campaigns waged against it, member defections, offers of amnesty, and the loss of public support. The rebellion eventually ran out of steam and withered away after the death of the main leader, Sekarmadji Maridjan Kartosuwirjo. However, though the West Java rebellion was defeated, the idea of establishing an Islamic state in Indonesia persisted, and it continues to inspire Islamist activists to this day.