 Querubin has been an active participant in various military operations during the ongoing CPP-NPA-NDF rebellion and the Moro conflict.He is credited with the neutralization of various rebel leaders of both the Communist Party of the Philippines-New People's Army and the Moro National Liberation Front, including CPP-NPA provincial chairman Jessie Rafael in 1981, four MNLF commanders in 1983, the NPA commander known as "Ka Ninong" and MNLF commander Racquel Carreon, both in 1988.He is also said to have been involved in the rescue of Hans Kunzli, a Swiss national kidnapped by a group led by a former member of the Moro National Liberation Front.