When the clouds of World War Two began to loom in the 1930s, Britain decided to begin securing some of its more distant colonial outposts – places that might be of strategic importance in a future conflict. Fiji was once of these outposts – a vital point on the seagoing supply line from Europe and the Americas to Australia and Asia. Construction of coastal defense batteries began in the late 1930s, mostly using 6 inch MkVII naval guns. These batteries were constructed around the capital of Suva and the airfield at Nadi on the west side of the island.
Today we are at the Momi Bay Battery, just south of Nadi. This emplacement has been restored and is maintained as a public museum site by the Fijian government today. It houses two 6 inch guns (the King’s Gun and the Queen’s Gun, colloquially), and originally also included an optical rangefinder and various command and control buildings. It had a range of about 8 miles, and controlled one of the few natural approaches to western Fiji.
The guns here were only fired in anger once, and that was actually at an unidentified sonar contact in the Bay. No evidence of an enemy vessel was ever found, and it ended up just being a brief reconnaissance by fire, so to speak. By later in the war, the threat of Japanese invasion had passed, but Fiji remained an active part of the war effort, as a transportation hub and a site for soldiers to get some R&R outside of combat duties. This led to the creation of the successful tourist economy which remains vibrant today on the island.
More details on the Momi Bay emplacement can be found here:
This paper by Allison Young provides a good overview of the wartime military preparations on Fiji.