During the Japanese occupation of the islands in World War II, there was an extensive Philippine resistance movement (Filipino: Kilusan ng Paglaban sa Pilipinas), which opposed the Japanese and their collaborators with active underground and guerrilla activity that increased over the years. Fighting the guerrillas – apart from the Japanese regular forces – were a Japanese-formed Bureau of Constabulary (later taking the name of the old Philippine Constabulary during the Second Republic), the Kenpeitai (the Japanese military police), and the Makapili (Filipinos fighting for the Japanese). Postwar studies estimate that around 260,000 persons were organized under guerrilla groups and that members of anti-Japanese underground organizations were more numerous. Such was their effectiveness that b