Today known as Taiwan, Formosa is a large island (14,000 square miles) located off the southeast coast of the Chinese mainland. It had been part of the Japanese Empire since the Sino-Japanese War of 1896, and by 1941 it had sizeable military bases and some industrial development. It supplied Japan with most of its sugar (something like a million tons a year) and small amounts of bauxite. The terrain is mountainous except for the western coastal plain, where most of the population lives, and the climate is subtropical. The most important cities were Taipeh and Takao (Kaohsiung).
References
The Pacific War Online Encyclopedia (c) 2006 by Kent G. Budge. Index