The Tragedy of Cemethuk at October 18th 1965 raises a question, “Why do the communists of Karangasem could slaughter Pemuda Ansor of Muncar, but they couldn’t touch the santris of Canga’aan?”. Because, geographicly, the distance between Karangasem and Muncar is about 30 km. Whereas, the distance between Karangasem and Canga’an is only 4 km. This research aims to find out the kind of defense system which used by the santris of Canga’an, so that they could saved from the anarchism that the communists of Karangasem made.This research used Historical Research Method. Which are Heuristic, Source Criticism, Interpretation, Hypothesis, and Historiography. With this method, it can be known that the santris of Canga’an didn’t use phisycal defense system. But instead, they only relying on dzikir and obey what kiyai said, not to join the movement of PKI’s members and sympathizers extermination, after G-30S/PKI affair in Jakarta.