Corregidor is an island located at the entrance of Manila Bay in the southwestern part of Luzon in the Philippines, and is considered part of the Province of Cavite. Due to this location, Corregidor has historically been fortified with coastal artillery batteries to defend the entrance of Manila Bay and Manila itself from attacks by enemy warships. Located 48 kilometres (30 mi) inland, Manila is the nation's largest city and has been the most important seaport in the Philippines for centuries, from the colonial rule of Spain, Japan, and the United States, up through the establishment of the Third Philippine Republic in 1946.

Manila Bay is a natural harbor that serves the Port of Manila, in the Philippines. Strategically located around the capital city of the Philippines, Manila Bay facilitated commerce and trade between the Philippines and its neighboring countries, becoming the gateway for socio-economic development even prior to Spanish occupation. With an area of 1,994 km2 (769.9 sq mi), and a coastline of 190 km (118.1 mi), Manila Bay is situated in the western part of Luzon and is bounded by Cavite and Metro Manila on the east, Bulacan and Pampanga on the north, and Bataan on the west and northwest. Manila Bay drains approximately 17,000 km2 (6,563.7 sq mi) of watershed area, with the Pampanga River contributing about 49% of the freshwater influx. With an average depth of 17 m (55.8 ft), it is estimated to have a total volume of 28.9 billion cubic meters. Entrance to the bay is 19 km (11.8 mi) wide and expands to a width of 48 km (29.8 mi). However, width of the bay varies from 22 km (13.7 mi) at its mouth and expanding to 60 km (37.3 mi) at its widest point.