Unfortunately we only had the best part of a day on Rottnest Island. I would recommend that others at least spend two nights/three days on the island as there is a lot to see. This post is for wargamers and covers the importance of Rottnest Island as part of “Fortress Fremantle” during WW2. It is not well known that the Port of Fremantle was the second largest submarine base in the Pacific during WW2 only to Pearl harbour itself.

During World War II, Rottnest Island changed from a popular holiday spot to an important military base, serving as part of the Fremantle Fortress. From 1940 to 1945, the island was off-limits and staffed by thousands of Australian Army, Navy, and Air Force members. Its role was to protect the important Fremantle port, a key submarine base for Allied forces, from sea attacks.

The gun coverage from Garden Island (still a major Australian Naval Base) on the left, and Rottnest Island on the right was extensive with multiple overlapping arcs of fire.

The island was strategically important due to its strong coastal artillery. The main defense, the Oliver Hill Battery, had two powerful 9.2-inch naval guns, which are the only intact ones of their type in Australia. These guns could hit enemy warships from up to 28 kilometers away, keeping threats far from the mainland. A smaller Bickley Battery with two 6-inch guns protected the channel between Rottnest and Carnac Islands. Supporting this firepower was a network of infrastructure that included a railway for ammunition transport, several searchlight emplacements, and a four-story Battery Observation Post at Signal Ridge, which coordinated gunfire for all batteries in the Fremantle Fortress. All of these facilities were built by the Australian Army Engineers.

Signal point is dominated by the Wadjemup Lighthouse which served its primary function as a lighthouse, while the Signal Station focused on military communication with incoming vessels, but the whole location became a crucial defense point during WWII. 

The WRANS House

While island defense was largely a male role, women had an important but often ignored part. The Women’s Royal Australian Naval Service (WRANS) were vital for defense, freeing men to focus on combat, and operated the Port War Signal Station at Signal Ridge, communicating with ships for quick threat responses. Their living quarters, WRANS House, was also located at Signal Ridge and is still in existence today.

The Signal Station operated by the WRANS

The four story Command Centre operated by AWAS

The Australian Women’s Army Service (AWAS) members tracked enemy ships at the War Signal Station operations tower and also supplied data for the guns from underground rooms at Oliver Hill. This command center coordinated gunfire for all batteries across the Fremantle Fortress.

In the final years of the war, the island transitioned from a military site to a Prisoner of War (POW) hostel, housing Italian POWs who worked on dismantling defenses and restoring tourist facilities, reflecting a shift towards post-war recovery.

Unfortunately I was only able to visit signal hill but there are other important WW2 installations restored and some repurposed.

Kingston Barracks

The Oliver Hill Battery with its two 9.2-inch naval guns

The railway today (above) and during WW2 (below)

Rottnest Island had a railway during World War II for transporting supplies to the Oliver Hill gun battery, which defended Fremantle; it is now the Captain Hussey train offering tours of the preserved military site.

The six inch guns at Bickley battery were decommissioned, but one can bbe seen outside Kingston Barracks, and the other can be found on the mainland at the Leighton Battery on Buckland Hill, Mosman Park, almost directly opposite Bickley Point.

Throughout the Island there are many walking trails where you can uncover many other military defence installations.

As you can see there is much more “important stuff” to see on the island.