Wil Hamers, Party Apple and the Dutch Catalina intelligence missions
On 13 January 1945, a Dutch Catalina flying boat approached an isolated stretch of the east coast of Japanese-occupied Borneo.
On board were eight NEFIS intelligence agents — four Dutch and four Indonesian servicemen — together with two rubber boats, radios, weapons and supplies packed into sealed petroleum tins.
Their destination was a point about 90 kilometres south of Tarakan, the strategically important oil-producing island off the north-east coast of Borneo in the Netherlands East Indies.
Their mission was to gather intelligence about Japanese forces and possible landing areas ahead of the planned Allied invasion of Tarakan.
At the controls was Dutch naval aviator Wil Hamers. The intelligence party had come from Cairns, where NEFIS III operated its secret training centre at the Z Experimental Station. Behind them lay the wider Dutch military and intelligence organisation operating from Australia, including the NEFIS headquarters at Camp Columbia in Brisbane.
Ahead lay Japanese-occupied territory.
The operation provides a remarkable glimpse of how the Dutch secret war from Australia was actually fought.
Wil Hamers – from merchant shipping to naval aviation
Wil Hamers was born in 1912 and trained at the nautical college on Texel before joining the Stoomvaart-Maatschappij Nederland. His first voyage took him to Batavia in the Netherlands East Indies.
During the war he became a pilot-observer with the Marine Luchtvaart Dienst (MLD), the Royal Netherlands Navy’s air service.
By 1944, after extensive operational flying in the Southwest Pacific Area, Hamers was transferred to an MLD detachment in Australia undertaking secret missions for Section III of the Netherlands Forces Intelligence Service — NEFIS III.
Hamers later recalled these experiences in an interview preserved in the Interview Collection Dutch Veterans of the Netherlands Veterans Institute. His recollections provide a rare first-hand account of what it was like to fly NEFIS agents from Australia into enemy territory.
NEFIS III and the secret war
The Netherlands Forces Intelligence Service had been rebuilt in Australia following the Japanese conquest of the Netherlands East Indies in early 1942.
Initially NEFIS concentrated primarily on gathering and analysing intelligence and maintaining security among Dutch forces in Australia. In April 1943 it was reorganised and a third section, NEFIS III, was established specifically for special intelligence and clandestine operations.
The task was formidable.
Unlike some European resistance organisations, the Dutch administration in the NEI had not established a substantial stay-behind intelligence network before the Japanese invasion. Agents therefore had to be inserted back into an enormous occupied archipelago and somehow establish contacts, gather information and communicate with Allied headquarters.
Initially, submarines were extensively used to land parties secretly.
The results could be disastrous.
Japanese counter-intelligence was effective, while the political and social situation inside occupied Indonesia had changed dramatically. Some agents were betrayed soon after landing. Capture could mean interrogation, torture and execution.
NEFIS therefore needed not only courageous volunteers but better training, better regional knowledge and different methods of inserting them.
The secret school at Cairns
An important part of that system developed at the Z Experimental Station at Mooroobool near Cairns.
Originally established in 1942 as an Allied special-operations training, communications and staging establishment, ZES had included Dutch and Indonesian personnel from its earliest period. Following the intelligence reorganisation of 1943, the Cairns facility increasingly became associated with NEFIS III.
Here Dutch and Indonesian agents could be trained and prepared before being sent back into Japanese-held territory.
By the time Hamers began flying NEFIS missions, the training centre was headed by Captain Vic de Bruyn — the remarkable Dutch colonial official sometimes called the “Jungle Pimpernel”.
De Bruyn brought something particularly valuable to the school: recent personal experience of surviving behind Japanese lines.
Vic de Bruyn – from New Guinea to Cairns
Before the war, Victor de Bruyn had been a government official in Dutch New Guinea.
When Japanese forces occupied the region, he withdrew into the interior around the Wissel Lakes, where he remained among local Papuan communities and continued supplying useful intelligence to the Allies.
In July 1944, NEFIS sent a Catalina into the Wissel Lakes to extract him.
De Bruyn was brought to Australia and placed in charge of the NEFIS III training centre at Cairns.
His appointment was significant.
Earlier Dutch intelligence missions had suffered partly because training developed elsewhere did not always adequately prepare agents for the geographical, social and political conditions of the Netherlands East Indies. De Bruyn had actually lived and operated for an extended period behind Japanese lines.
That experience could now be passed to the men being prepared at Cairns.
Catalinas become part of the intelligence system
The Catalina flying boat was particularly useful for this clandestine work.
Its long range and ability to land on water meant agents could be transported to remote coastal areas without requiring an airfield.
Hamers recalled collecting agents at Cairns and flying them towards their destination. Near the coast, the aircraft would land and the intelligence party would transfer its equipment into rubber boats.
The men then paddled ashore and disappeared into enemy-held territory.
Hamers would maintain radio contact long enough to establish that the party appeared to have reached safety before returning to base.
The plan was to come back later and retrieve them.
There was, however, no certainty that they would still be alive.
Party Apple
One of Hamers’ best documented missions was Party Apple.
By early 1945 the Allies were preparing to return to Borneo.
Tarakan was particularly important. The small island off Borneo’s north-eastern coast possessed valuable oilfields and an airfield and had been heavily fortified by the Japanese.
NEFIS III was ordered to obtain intelligence ahead of the planned Allied landing.
Party Apple consisted of eight men: four Dutch and four Indonesian servicemen. Its commander was Lieutenant Oscar Drijber.
The mission was to gather information from local people about Japanese strength and activity on Tarakan, identify possible landing beaches and routes inland and, if possible, establish a forward radio post.
An extraordinary commander
Drijber had already experienced an extraordinary war.
As a young Dutch army officer he had fought the Germans during the invasion of the Netherlands in May 1940.
After the Dutch capitulation, he refused to sign the declaration of honour under which Dutch officers promised not to take further action against Germany. He was consequently sent to Germany as a prisoner of war.
In September 1941 he escaped from the supposedly escape-proof Colditz Castle and eventually reached Britain through Switzerland.
There he underwent commando training before ultimately volunteering for NEFIS III and travelling to Australia.
But Drijber had an obvious disadvantage.
Half its members were Indonesian.
He had never lived in the Netherlands East Indies and spoke little Malay.
Hamers himself questioned the decision to place him in command of an intelligence party whose survival could depend upon understanding local people.
It illustrates one of the recurring difficulties facing NEFIS: finding volunteers who combined military skills, intelligence training, language ability and intimate knowledge of the enormous and culturally diverse Indonesian archipelago.
Four Dutch and four Indonesian servicemen
The composition of Party Apple is therefore important.
This reflected the practical reality of NEFIS operations. Dutch intelligence depended heavily upon Indonesian and other locally knowledgeable personnel who possessed the languages, cultural understanding and geographical experience European operatives often lacked.
One of the Party Apple members was telegraphist W.F. Schenau, responsible for establishing radio contact once the party was ashore.
The eight men represented in miniature the multinational character of the intelligence organisation being operated from Australia.
Landing on Borneo
On 12 January 1945 Hamers’ Catalina reconnoitred the intended landing area near Cape Tandjoengselor.
The original location was judged unsuitable, so the following day Party Apple was landed approximately 20 kilometres further north, closer to Tarakan.
Hamers remembered the party and all its equipment arriving from Cairns and being loaded aboard the aircraft.
Once on the Borneo coast, the men took their rubber boats and supplies ashore.
Then the problems began.
Soap with the biscuits
Party Apple’s supplies had been packed into sealed petroleum tins of the type traditionally used by KNIL patrols.
The arrangement may have made sense for conventional military expeditions in the NEI, where porters could carry the tins.
Party Apple had no such porters.
The eight agents had to carry everything themselves.
Worse, the tins were not adequately marked. The men could not easily determine what each contained without opening it.
Hamers recalled that the problem became so absurd that the agents resorted to drastic methods to get into some containers. Supplies that should logically have been separated had been packed together.
Drijber was furious.
In his subsequent report he sarcastically complained about soap being packed with biscuits and directed his anger towards those responsible at Camp Columbia in Brisbane, where NEFIS and other Netherlands East Indies organisations were headquartered.
The episode is amusing in retrospect, but it exposed a serious problem.
A clandestine intelligence party operating without conventional logistical support required equipment designed specifically for that mission. Applying ordinary KNIL procedures could create unnecessary burdens and potentially endanger the agents.
Radio problems
There was another difficulty.
Telegraphist Schenau attempted to establish communications with the Allied intelligence station on Morotai but was unable to make contact. Both the portable ATR4A radio and the NEI set were tried without success.
Morotai is a small island in the northern Moluccas (Maluku), in what is now Indonesia. Allied forces had captured it in September 1944 and rapidly developed it into a major forward air, naval and logistics base for operations towards the Philippines and the Netherlands East Indies. For NEFIS, Morotai provided an important forward intelligence base much closer to Japanese-occupied territory than Australia.
After Party Apple returned to Morotai, the equipment was tested again. The radios themselves largely worked, although a problem was discovered with the pedal generator for the NEI set. Research into the operation suggests that propagation conditions may also have contributed to the communications failure.
For an intelligence party, failure of radio communications was potentially critical.
Information gathered behind enemy lines had little immediate military value if it could not be transmitted to the commanders who needed it.
A difficult local environment
Drijber also encountered another of the problems that had plagued earlier NEFIS missions.
Party Apple needed assistance from local inhabitants.
From the landing area Drijber contacted the head of a nearby kampong inhabited by Bugis people originating from Celebes.
He soon concluded that they were unwilling to cooperate.
This was a fundamental intelligence problem.
NEFIS had initially underestimated how much conditions within the Netherlands East Indies had changed during three years of Japanese occupation. Indonesian nationalism had developed rapidly, Japanese intelligence networks were extensive, and local communities had many reasons to be cautious about assisting agents claiming to represent the returning Dutch administration.
For clandestine parties, assumptions about local loyalty could be fatal.
Eleven days behind enemy lines
Party Apple nevertheless remained ashore for eleven days.
The mission achieved only part of its objectives, but the party did gather information, including intelligence concerning the strength of the Japanese garrison on Tarakan.
On 24 January Hamers returned with the Catalina.
For the aircrew, successfully finding a party alive after days inside enemy territory was an enormous relief.
Hamers remembered sending his sergeant-pilot ashore in a rubber boat with a particularly welcome item for the exhausted agents: a bottle of cold beer.
The eight men were brought aboard and flown to Morotai.
From Borneo to Allied intelligence
The mission did not end when the Catalina left the Borneo coast.
At Morotai, the information gathered by Party Apple entered the wider Allied intelligence system.
The men were questioned by intelligence personnel and reported what they had discovered about Tarakan and conditions in the area.
One incident again illustrates the multinational and sometimes confusing character of the Allied war.
An Indonesian member of Party Apple, suffering from malaria, collapsed near the beach after leaving the aircraft. He was subsequently detained because Allied personnel mistook him for a Japanese infiltrator.
He was eventually brought into the intelligence debriefing before the misunderstanding was resolved.
The episode is almost comic, but it also illustrates how Indonesian personnel serving within Dutch intelligence could be perceived by Allied servicemen unfamiliar with their role.
The Allies return to Tarakan
A little more than three months later, on 1 May 1945, the Allied assault on Tarakan began.
The main force was Australia’s 26th Infantry Brigade.
Alongside the Australians came a company of the KNIL.
For the Netherlands this had particular significance. It was the first time since the surrender of the Netherlands East Indies in March 1942 that an organised KNIL unit participated in an Allied operation to recover NEI territory.
Party Apple’s intelligence had been gathered as part of the preparation for this return.
The mission itself was modest. It did not determine the outcome of the Battle of Tarakan, and its difficulties demonstrate the limitations under which NEFIS parties operated.
But that is precisely what makes the story valuable.
It shows how intelligence was actually gathered: by small groups of volunteers being landed on isolated beaches, attempting to establish contact with local communities, struggling with radios and equipment, and trying to survive long enough to report what they had learned.
From Australia into the secret war
Wil Hamers later regarded his period flying for NEFIS III in 1944 and early 1945 as one of the most interesting parts of his wartime service.
His story connects many elements of the Dutch wartime presence in Australia that can otherwise appear as separate histories.
NEFIS headquarters operated from Australia. Agents were trained at the Z Experimental Station in Cairns. Dutch and Indonesian personnel worked together in clandestine parties. The Marine Luchtvaart Dienst supplied aircraft and crews capable of inserting them into remote territory. Camp Columbia in Brisbane formed part of the administrative and logistical system behind them. Morotai provided a forward Allied base where the intelligence they gathered could be assessed.
Party Apple travelled through that entire network.
It began with preparation in Australia and ended with intelligence being delivered to Allied commanders preparing to return to the Netherlands East Indies.
The mission also reveals the imperfections of that system: unsuitable equipment, communications failures, shortages of personnel with local knowledge and uncertainty about the attitude of Indonesian communities towards the returning Dutch.
Yet eight men were successfully landed behind Japanese lines, gathered intelligence and were brought out alive eleven days later.
The Catalina that carried them from Cairns to Borneo therefore provides an unusually tangible picture of the secret war being conducted from Australia.
Behind the major Allied campaigns were small operations such as Party Apple — Dutch aircrew, Dutch and Indonesian intelligence agents, Australian bases and Allied headquarters all contributing to the attempt to penetrate an occupied archipelago.
It is another largely forgotten chapter of Dutch-Australian-Indonesian cooperation during the Pacific War.
Paul Budde August 2026
Sources and further reading
The principal source for Wil Hamers and Party Apple is the Netherlands Veterans Institute article based on Hamers’ testimony in the Interview Collection Dutch Veterans:
Netherlands Veterans Institute – Vliegboten en geheime agenten in de Indische Archipel
The detailed reconstruction of NEFIS radio operations provides additional information about Party Apple, the Y-87 Catalina, telegraphist W.F. Schenau, the mission’s communications problems and its intelligence objectives:
For the wider background to NEFIS III, the Z Experimental Station at Cairns and Dutch-Australian-Indonesian intelligence cooperation, see the related DACC articles:
The Forgotten Dutch and Indonesian Story of Cairns’ Z Experimental Station
Dutch, Australian and Indonesian Agents: The NEI Section of Australia’s Secret War [existing
WWII Netherlands Forces Intelligence Service operating from Australia
Julius Tahija was one of the few NEI men who received the Netherlands’ highest military order
