This document, Terrain Handbook 50, is a classified military intelligence report prepared by the Allied Geographical Section (AGS) of the Southwest Pacific Area (SWPA), operating under the command of General Douglas MacArthur. Dated November 29, 1944, the handbook was published during the crucial period of operational planning for the invasion of Luzon, the main island of the Philippines.
Terrain handbook 50: NW Luzon (Philippine series)
