The older system of direct fire, known as the Battery System of fire (or Close Defence), was still to be used, if the enemy came within visual range of the battery. The other batteries would then open fire on the target using the indirect method of fire. Both systems required the use of a separate plotting room, thus for each battery a Fortress Plotting Room and a Battery Plotting Room were required.
At the end of WW1 Wellington had several batteries active. Only one, Fort Dorset, was mounted with modern weapons. The older batteries were finally scraped during the 1920s, many having their gun pits converted to hold ammunition. With the Great Depression occurring in the late 1920s little was done to improve NZ's Defences.
In a scheme of Imperial Defence laid down by the War Office in London, Wellington was classed as a defended port, with defences specified as one 6-inch battery. The main threat to Wellington was seen to be a raid by a cruiser to bombard the port, not an invasion. Noting the increase in cruiser construction by the worlds navies, this threat was upgraded to one or more ships. Accordingly it was decided to upgrade the numbers of batteries at defended ports from one to two. It was at this time that Palmer Head was constructed.
