'Ferdinand' (i) was Allied (primarily Australian) network of coastwatchers established in the period following World War I and completed in March 1943 to operate on Japanese-held islands throughout the Philippine islands group and the South Pacific region (1941/44).

This system of observers consisted of civilians and some military volunteers who radioed reports on Japanese ship movements. First established by the Royal Australian Navy after World War I to provide a surveillance capability over the long unguarded coastlines of Australia and its neighbouring islands, the Islands Coastwatching Service was headed in September 1939 by Lieutenant Commander Eric Feldt, who was instructed to complete the network as swiftly as possible. By mid-1941 Feldt had established more than 100 transmitter-equipped stations covering some 2,500 miles (4025 km) of coast between the western borders of Papua to the New Hebrides.

Many of the people operating these stations had to be evacuated before the arrival of Japanese forces in the early months of 1942, but the proved reliability of their early information led to an expansion of the service and by March 1943 the Solomon islands group had a chain of coastwatcher stations. The codename 'Ferdinand', after a Walt Disney cartoon bull who rested under a tree smelling flowers but did not fight, served as a reminder that it was the task of a coastwatcher not to fight 'but to sit circumspectly and unobtrusively, gathering information'. Most coastwatchers adhered to this concept, but if threatened by Japanese patrols, with the help of loyal local people they had no hesitation in destroying them.

Most coastwatchers were Europeans who had settled on the islands, and all but the sole woman operator were eventually given a service rank in an attempt to give them the possible protection of the Geneva protocols if they were captured.

When the organisation was expanded, it came also to include service personnel from Australia, New Zealand, the USA, and the Solomon Islands Protectorate Defence Force, as well as native civilians.

In July 1942 coastwatchers in General Douglas MacArthur’s South-West Pacific Area command became part of the newly formed Allied Intelligence Bureau (AIB) but those in the South Pacific Area remained part of the Australian Naval Intelligence apparatus. The resulting chain of command was complicated but worked well as Feldt was put in charge of both areas, and was therefore in the position to feed information to both AIB and the South Pacific Area commander.

As US plans to land on Guadalcanal in the Solomon islands group matured as 'Watchtower', the information sent by coastwatchers stationed in the area became increasingly useful. Details of Japanese strengths and movements, and regular reports on weather patterns, all contributed to the success of the landings on 7 August 1942. Two coastwatchers acted as guides for the contemporary 'Ringbolt' landings on Tulagi, and once US Marine Corps forces were ashore there and on Guadalcanal other coastwatchers on Bougainville island farther to the north-west along the chain of the Solomon islands transmitted vital warnings of Japanese air attacks mounted from New Britain and New Ireland. In the months of bitter fighting which followed on Guadalcanal, these coastwatchers constituted so important a warning system that the US commander of the South Pacific Area, Admiral William F. Halsey, later said that it was the coastwatchers who saved Guadalcanal, and that Guadalcanal saved the South Pacific.

During the Guadalcanal campaign a base radio station was established there so that outlying coastwatchers could report their information direct. Other coast watchers were landed on Vella Lavella and Choiseul islands to report Japanese shipping movements, and during the Japanese build-up in October 1942 for the recapture of Guadalcanal they were able to send detailed reports which helped thwart the intended offensive. The coastwatchers and their indigenous helpers also organised an invaluable rescue service; the number of airmen rescued from various islands was impressive: six from Guadalcanal, 28 from Santa Isabel, 22 from New Georgia, eight from Rendova, 31 from Vella Lavella, and 23 from Choiseul.

The coastwatchers also charted safe waters for the movements US supply ships operating along the north-east coast of New Guinea between Milne Bay and Buna, provided early warning of air attacks when New Britain was invaded, helped to organise guerrilla actions behind the Japanese lines, and at Hollandia mounted a pre-invasion reconnaissance. By October 1944 only isolated pockets of Japanese remained where the coastwatchers had been operating, and the service, which had suffered a high casualty rate, was disbanded.