Bombay was the second largest urban area in the British Empire in term of population. The town was along a four mile island, about one mile wide. The closest potentially hostile ports were Diego Squarez (2,200 miles) and Saigon (2,490 miles). The Harbour was enclosed by Bombay Island on the west, Trombay Island in the northwest, Elephanta and Carija Islands and the mainland in the east. The ridges of Mahaluzmi, Malabar Hill and Coloba overlooked parts of the harbour and fortifications were naturally placed here.
In 1879 there were a number of coastal defence batteries with open barbette emplacements including those the following:
Mahaluxmi Battery with two 10-inch RML guns. By 1891 upgraded to one 10-inch BL gun, two 6-inch BL guns and two 10-inch RML guns
Malabar Point Battery with two 10-inch RML guns and three 7-inch RBL guns. By 1891 upgraded to one 10-inch BL gun, two 6-inch BL guns and two 10-inch RML guns
Colaba Point Battery with three 9-inch RML guns. By 1891 upgraded to two 10-inch BL guns, two 6-inch BL guns and two 10-inch RML guns
Middle Ground Battery with three 9-inch RML guns. By 1891 upgraded to two 10-inch BL guns, three 6-inch BL guns and three 6-pdr Q.F. guns
Oyster Rock Battery with two 10-inch RML guns, eight 9-inch RML guns and two 7-inch RBL guns. By 1891 upgraded to two 10-inch BL guns, three 6-inch BL guns and three 6-pdr Q.F. guns
Cross Island Battery with twelve 7-inch RBL guns. By 1891 upgraded to two 12.5-inch RML guns, two 6-inch BL guns and two 6-pdr Q.F. guns
Royal Commission Appointed to Enquire into the Defence of British Possessions and Commerce Abroad chaired by the Earl of Carnarvon, 1879 to 1882 designated Bombay as a defended Commercial Port.