The Lahad Datu incident makes a re-examination of Philippine claim to Sabah compelling. During the twenty-year Marcosian rule, the Sabah claim somewhat defined Philippine foreign policy in its relation to Malaysia and to ASEAN. It was made complicated by the formation of a Moro rebellion. What is the role of Malaysia in the secessionist movement in the south? This article examines this in light of “old” and “new” sources, as it tries to explore a possible conspiracy between Malaysian leaders, the Liberal Party, and some Moro leaders behind the rebellion in Mindanao and Sulu, and its connection to Sabah.