Thirteenth Air Force has never been stationed in the continental United States; it is also one of the oldest, continuously active, numbered air forces. It engaged in combat in the Pacific Theater during World War II. Since World War II, it has provided air defense in the Far East, primarily the Philippines, until the 1991 eruption of Mt. Pinatubo forced the closure of Clark AB. Numerous Thirteenth Air Force organizations participated in Southeast Asia combat operations in the 1960s and 1970s.