This article examines the utility of opportunity theory, framing analysis, and symbolic politics theory in explaining the causes of ethnic war, focusing on the 1970s Mindanao case. Opportunity variables are present as expected, but process-tracing shows they do not operate according to the hypothesized mechanisms. The framing approach identifies several important dynamics. The resonance of frames was influenced by the salience of the issue highlighted, the narrative fidelity of the frame to preexisting cultural beliefs, the credibility of leaders proposing them, and processes of frame bridging. Symbolic politics theory offers the most complete explanation, embracing most of the alternative explanations’ insights while filling in their logical gaps. The symbolist analysis begins with group myths justifying hostility on both sides, the result of past Christian–Muslim warfare. Combined with fears of group extinction, opportunity factors, and hostile popular attitudes, these myths enabled group elites to manipulate emotive symbols to justify mobilization against the other group, creating a security dilemma spiral that resulted in the outbreak of war.