This article discusses New Zealand coastline coast-watching services during the Second World War, particularly recording the Post Office contribution to that effort.

Prior Planning

[NZCW] In 1929 the Navy had drawn up a scheme for maintaining a watch from the coasts of New Zealand, using the services of the Royal New Zealand Naval Volunteer Reserve. In 1935 the scheme was modified to pass over the duty of actual coast-watching to trustworthy civilians who were to report to the District Naval Intelligence Officers in the four main cities, the whole organisation being under the operational control of the New Zealand Naval Board.

[NZCW] The scheme for location and maintenance of coast-watching posts throughout New Zealand was further elaborated during 1938 and 1939, provision being made for fifty-eight stations operating a 24-hour watch. On the outbreak of war the scheme was smoothly brought into action. In March 1940 there were sixty-two stations, maintained by service and civilian personnel, at different points round the coast, many of them in out-of-the-way positions.

Site Evolution

[NZCW] In later years of the war the coast-watching organisation was several times modified. The number of stations fluctuated; some were abolished altogether and aerial patrols substituted. Stations were established in the Chatham Islands and also on Norfolk Island and the Kermadecs. In 1943 a number of radar stations had been established in New Zealand and on outlying islands: these carried out duties analagous to coast-watching but by a different means. By 1944 twenty-one coast-watching stations were retained on a care and maintenance basis only; that is, they were left fully equipped and could be quickly manned and immediately used in an emergency.

Communication

[NZCW] The more important accessible stations were linked to the Area Combined Headquarters by direct line telephone. Others, in more remote positions, reported by radio.

Personnel

[NZCW] Although operational control was centered in the Navy, the coast-watchers might be civilians or might belong to the Navy (at port war signal stations), the Air Force (at some radar stations), or the Army (at many coast-watching and some radar stations). The approaches to some ports were equipped with additional reporting devices which were directly controlled by the Navy. In spite of this diversity the system functioned efficiently, and the naval authorities were able to get rapid information of all shipping movements.

 

Post Office Contributions

The principle contribution of the Post and Telegraph Department to coast-watching (and the whole war effort) was two-fold - these relating to equipment supply and to the provision of trained personnel.

The war years were a time of significant technology development, and while New Zealand had early radio equipment in use, the prime source of technical radio knowledge and capability for nearly all Government departments was the Post Office. Within the Post Office the Engineers Office had introduced spark transmitter and crystal set technology to the country since commissioning of its first radio stations in 1913 (Awanui Radio, Auckland Radio, Wellington Radio, Awarua Radio and Chatham Islands Radio). As the Post Office evolved those services it stayed in the front lines of radio development and, through its Radio Section in Wellington, shared its knowledge and guided equipment development and purchases across Government.

Radar

Therefore, when war was announced Radio Section officers were selected to join other countries at briefings in the UK to learn about the new (and very secret) development of radar technology. Subsequently, in a controlled-access laboratory in Radio Section, officers worked on building prototypes of New Zealand's own radar systems. In conjunction with government scientists these early developments were ultimately used as the basis of New Zealand's radar capability.

A radar-testing experiment was to cause them some concern when a radar overlooking Cook Strait recorded the passage of ships sailing across an area of dry land. In a conversation in a survey office (conducted in whispers) an outburst of laughter from the senior surveyor revealed that the maps in use were still those created by Captain Cook, and that he had included some chart anomalies which had yet to be corrected. Relocating a peninsula on the map fixed the radar issue and confirmed how accurate the systems could be.

The development of radar in the early war years explains why the use of radar sites was not factored into the Navy's earlier coast-watching plans. They were also an example of how new technology could augment the coast-watcher capability.

Radio Capability

At the outbreak of war the Post Office had a series of coast radio stations around the country. These sites were established to provide commercial communications ability for coastal and international shipping, plus for point-to-point communications with New Zealand island territories and other countries, principally with our closer neighbors Australia and Fiji. This meant that Post Office radio operators could be available to man or train staff at coast-watching sites, and that its equipment stores and pre-planning with radio manufacturers could support remote coast-watching needs.

Signal Monitoring

The Post Office coast stations were ideal for performing another function - looking for the presence of foreign shipping by listening for their radio transmissions and reporting any traffic to a central command. This was an activity classed as 'signals intelligence' or SIGINT and was conducted as a classified (secret) activity. SIGINT monitoring again expanded the coast-watching capability significantly, and was used very effectively in support of military operations in the pacific. Both Awarua Radio and Musick Memorial Radio stations were under guard presence during the war years and conducted SIGINT activity.

In terms of routine coast-watcher radio monitoring, both Chatham Islands and Norfolk Island were designated coast-watcher sites (refer Site Evolution above). This placed the civilian radio staff on these islands on the same footing as their contemporaries deployed to Pacific islands.

Radio Direction Finding

A further technology used in support of an 'enlarged' perspective of coast-watching was the use of radio direction finding (DF). At the lead-in to the war years there were two prime direction finding systems based on their frequency of use.

In those pre-GPS location-finding days a 'medium wave'  system was used for lower frequency signals. This wave band was predominantly used within New Zealand for civilian aircraft guidance, and for safety of life at sea based on shipping using the 500kHz (MHz) radio frequency for distress messages.

The second system utilised 'short wave' or 'high frequency' direction finding which was an advance on medium wave, provided more precise bearings and was particularly effective for night-time use. High Frequency direction finding (HFDF) was mainly used for aircraft navigation support by tracking international flying boats between New Zealand and Australia or from America via the Pacific islands.

Awarua Radio provided support to Captain Mercer, the owner of a West Coast aircraft company. He was tasked to carry out regular flights down the West Coast to observe shipping - particularly anything that might be in the deep fiords to the south. The support given was to maintain radio contact with him and to provide directional bearings for him to assist his navigation.

With the entry of Japan into the war, Awarua's HFDF role became more urgent, particularly as Japan had deployed a large submarine fleet. As New Zealand's prime SIGINT site, Awarua's operators were constantly aware of the need to locate submarine traffic on the wave bands, and to pass that information to the HFDF operator for location finding. Awarua had technical control of the New Zealand HFDF network, could alert the other HFDF sites (Musick Radio, Waipapakauri near Kaitaia, and Suva, Fiji) and rapidly obtain bearings for providing to the central tracking office in Wellington.

Using the New Zealand HFDF system in a coast-watching sense, Japanese submarines were tracked off the coast of Australia prior to their mini-submarine attack on Sydney Harbour, a large submarine with seaplane capability was tracked through Cook Strait and up the east coast of the North Island. In 1939 Awarua tracked the movements of the German cruiser Admiral Graf Spee in the Atlantic ocean and helped alert the British naval forces about its position.