During World War II, the Japanese established a defensive perimeter in the Indian Ocean region. This perimeter was meant to protect their territories and supply lines in Southeast Asia. Rangoon, Burma (now Myanmar) was an important city within this perimeter and served as a major hub for Japanese operations in the region. It was strategically located and provided the Japanese with a base from which they could launch further offensives and control the surrounding areas. The other options, Darwin, Australia, Truk in the Carolines, and Rabaul on New Britain, were also significant locations during the war, but they were not specifically part of the Japanese perimeter in the Indian Ocean.