In 1934 the British War Office advised the New Zealand Army that the whole of the Wellington harbour area could be protected from enemy attack by the construction of a 9.2-inch battery on 'point 1181 K6431', or Wrights Hill.
During this period the key threat to Wellington harbour was the increasing number of cruisers armed with 8 or 11-inch armaments being constructed by potentially hostile nations. Many of Wellington's coastal defence batteries were initially constructed during the 'Russian Scare' of 1885 and, although upgraded and added to, were no longer sufficient to protect the harbour from the increased range of enemy guns. The New Zealand Army and the War Office debated the best means of combating the perceived threat. On the one hand, two 6-inch 45-degree guns with range-finding equipment could be installed at Palmer Head and Dorset Point for approximately £95,000. On the other, two 9.2-inch guns installed at Wrights Hill would provide 'adequate defence of the whole harbour area' for £125,000. While the cheaper option was preferred and a battery was constructed at Palmer Head, the concept of a battery at Wrights Hill had been born. The Army continued to plan for the installation of the 9.2-inch battery. Detailed planning and costing was carried out, but in 1937 the Army's budget bid that would allow for its construction was rejected for the second time on the grounds of cost.
It was the outbreak of the Second World War in 1939 that finally provided the necessary impetus for the construction of the Wrights Hill Fortress. In 1939 the construction of 9.2-inch battery to protect Wellington was immediately authorised, as was the construction of an additional 6-inch battery at Opau, and the laying of a minefield, boom and underwater detection devices across the harbour entrance. Yet the immediate authorisation was not sufficient to ensure that work commenced at Wrights Hill, and British manufacturers who were unable to say when the guns would be delivered caused delays.
It was not until 1941, with the outbreak of the war in the Pacific that the Wrights Hill Fortress became a priority. Possibly named after early settler and Farmer John Fortescue Wright, the bush-clad Wrights Hill had been farmed since the 1870s, and was still being used as farmland when the army finally purchased it for the battery in 1942. Although based on standard plans for 9.2-inch batteries developed by the British War Office, the Wrights Hill Fortress is unique. Instead of creating an above surface structure, the Public Works Department saved both time and money by using their knowledge of tunnelling to create an underground battery. The battery's distinctive semi-circular tunnels are based on the design developed for the Tawa Flat railway deviation completed in 1936. At the same time as the Wrights Hill plans were being developed, similar plans were also being created for three batteries designed to protect Auckland and Lyttleton harbours. Of the four, Wrights Hill was to be the most compact.
The battery was to consist of three gun emplacements, each of which would hold a 9.2-inch Mk XV guns on an Mk IX mounting. An underground magazine, a pump chamber and a war shelter serviced each emplacement. Reflecting the inclusion of female personnel in the army, the war shelters each had provisions for female staff in the form of separate female toilets. In addition, the battery was to be serviced by an engine room, plotting rooms, battery observation post, and a radio room. Outside the complex were a parade ground, and a miniature range building, which, once constructed, contained the only miniature range equipment constructed in New Zealand during the war. Due to the ever-constant shortage of funds, the construction of the Wrights Hill battery was let to a private company, Downer & Co. Ltd, and tunnelling commenced in early 1942. By September 1943, the company was running short of supplies and labour and the Public Works Department was called in to assist and given absolute priority. By the end of 1943 all excavations had been completed, and concreting work was well advanced. Yet work on the project was impacted by both the costs and developments in the war in the Allies' favour. In early 1944 its labour force was diverted to other projects and the third gun order was cancelled in June that same year. Despite this, the civil engineering part of the project was largely complete by June 1944 and the No.1 gun was installed three months later, with the second gun installation being completed shortly after. Around this time the decision was made later that year to complete the battery to the minimum standard required. Despite this, work on the project was not finally completed until 1947, two years after the end of the Second World War.
It was one of just two of the 9.2-inch batteries to be completed to any extent technically. With the end of the War, Wrights Hill was relegated to training purposes only. Its two guns had been test-fired in 1946, and 1947, blowing out a number of windows in the surrounding suburb of Karori. These tests were the only time they were used. All work on the complex had ceased by 1949, and in 1951 all training at the complex ceased. Six years later the battery was officially abandoned and its equipment was scrapped. The gun pits were filled in between 1960 and 1962. In 1988 the Karori Lions Club took on the role of guardians of the site following years of neglect. Volunteers cleaned up the area, removing the rubble from the gun emplacements, restoring the tunnels and re-equipping the facilities so that the site could become safe for the public to visit. The Wrights Hill Fortress Restoration Society, formed in 1992, aimed to 'restore and preserve the Wrights Hill Fortress as an historical monument for the benefit of the community'. The site is now part of a recreation reserve and is open to the public at various times of the year to allow the old to remember, the not-so-old to understand, and the young to learn about the measures taken by the Government to ensure the safety of its citizens at a time of conflict in multiple arenas of war.