“No rain without stopping, no war without ending,” according to conventional wisdom. War would cease to some point, but it may take different routes of terminating. Besides elimination and capitulation, negotiation is another route of ending the war peacefully. In many cases, negotiation that can produce a peace agreement is a rocky process, but it is possible to achieve. Indonesia is a case in point. The government and GAM (Gerakan Aceh Merdeka, Free Aceh Movement) finally signed a peace treaty in 2005 after almost three decades of civil war. So far, there have been no serious complaints about the implementation of the treaty, only minor ones. With the same factors that influence negotiation, the process may fail along the way. South Thailand is an example of this case. The government and Bersatu (United Front for the Independence of Pattani) remain at war albeit sporadically. This book compares Aceh as a case of sustained peace process and South Thailand as a case of collapsed peace process. It will contribute to our understanding why a peace process is sustained while others are disintegrated.