A look at Mindanao, the main southern island in the Philippines and a battlefield between government forces and Muslim rebels for more than three decades:

Population: 16 million. The island used to be largely Muslim before Christians from other parts of the Philippines began settling there in the 1950s. Now it is mostly Christian.

History: Mindanao was an independent sultanate until the Spanish arrived in the 16th century. Muslim resistance continued during the American colonial period and after independence in 1946. A full-scale rebellion erupted in the 1970s, claiming over 125,000 lives before the government and the main Muslim rebel group made peace in 1996. Another rebel faction, the Moro Islamic Liberation Front, continued to fight. The government is also battling communist guerrillas on the island.

Geography: Largely mountainous, Mindanao is the second-largest island in the archipelago, with 40,800 square miles. It accounts for about a third of the Philippines.

Economy: In addition to gold, Mindanao produces nickel, zinc and manganese. The island is the nation's leading producer of bananas, pineapple, corn, coffee and coconut for export. Other agricultural products include rubber, palm oil and cotton. Seaweed and tuna also are major exports. Despite the abundant resources, many islanders are among poorest in the country.

Rebels: The military estimates 12,000 Moro Islamic Liberation Front guerrillas operate on Mindanao. The Muslim extremist Abu Sayyaf group also is active in some areas.