We present a planner for the Combat Power Management (CPM) problem. In response to multiple simultaneous or sequential threats, the planner generates a set of local plans, one for each target considered apart, and then merges them by searching the space of global plans. The proposed plan merging solution serves also as an iterative plan repair process that resolves negative interferences (subaddivity) and exploits synergistic effects (superaddivity) among activities. The planner was developed as a component of a naval Command and Control system to support the warship command team in defending against Anti-Ship Missile threats. The planner is particularly suited for domains characterized by durative concurrent actions, with both superadditive and subadditive interactions, and probabilistic effects. It is implemented in a generic way, allowing it to address other application domains. We discuss the CPM application domain, describe the planner, and present experimental results.