No. 18 (Netherlands East Indies) Squadron (RAAF) "The Dutch Cleanser"

About This Unit

No. 18 Squadron Netherlands East Indies (RAAF)

As the Japanese drove south after the outbreak of unrestricted war in the Pacific on 7 December 1941, the Dutch Colonial possessions in the Netherlands East Indies came under pressure very quickly.

The NEI forces were scheduled to receive a range of aircraft from the USA under Lend Lease Agreement arrangements.

Included among these shipments were North American B-25 Mitchell and Douglas A-20 Havocs (known as Bostons in RAF / RAAF service) medium and light bombers respectively, as well as large quantities of light weapons and ammunition.

Many of the aircraft were diverted to Australia.  Large amounts of the light weapons and ammunition were requisitioned by 'Blackforce' when it was dropped in Batavia by the Orcades in early 1942, without their own weapons and equipment which was on another ship bound for Australia! That is the subject of another series of aritcles on this site.

As the British Dutch and Australian defences were progressively overrun by the Japanese in early 1942, Dutch airmen (many of whom were actually Naval aviators) who escaped to Australia  were brought together to form Dutch squadrons under RAAF command. First among these special squadrons was 18 (NEI) Squadron, formed at Canberra on 4 April 1942. Although nominally made up of Dutch nationals, the RAAF supplied many co-pilots, air gunners, bombardiers, photographers, and ground staff. The US provided supplies and equipment.

Engagement with enemy forces came early for 18 Squadron when, on 5 June 1942, B-25s attacked  and claimed to have sunk a 300-ton Japanese submarine off Sydney. This success resulted in the supply of 18 B-25s between August and September. In December the unit moved to MacDonald airstrip in the Northern Territory and began transforming the undeveloped site into a workable airbase. From January the squadron commenced offensive operation missions over Timor, the Tanimbar and Kai Islands.

The squadron moved to Batchelor airfield in the Northern Territory between April and May 1943. It commenced reconnaissance over Somniloguy Island, Tanimbar Island, and Ambon, and offensive operations on Penfoei, Koepang Harbour, and Dili. Mast-height attack on Japanese shipping and faulty delay-action fuses inflicted substantial losses during the period.

Between November 1943 and March 1944 18 Squadron was ordered to prevent Japanese reinforcements reaching the north-east part of Papua and New Guinea. Operations focused on attacking positions and seaborne traffic around Timor, Ambon, and the Kai and Aroe Islands. The sinking of over 25,000 tones of Japanese ships earned the unit the nickname "the Dutch cleanser".

The realities of operations were brutal.  Flights were long and by definition mainly over water.  Even technical problems over Australian territory were hazardous with a dearth of emergency landing options and large distances to traverse.  In the target area there was an ever-present risk from Japanese defences, either fighters, flack or both.  Downed crews might hope for retrieval by a comprehensive air sea rescue system headed by PBY Catalina flying boats, however escaping from a crippled aircraft over Japanese territory was most often a death sentence, with aircrew generally being summarily executed by beheading by their captors.

As the war progressed, the B-25’s were progressively modified for the specialist attacks they were undertaking.  ‘Skip Bombing’ was found to be the most effective technique against enemy shipping.  The technique had been perfected in New Guinea, against an old wreck off Port Moresby.  The concept of ‘skip-bombing’ was a low, flat approach to drop bombs short of the target in such a way that the bombs bounced off the water and struck nose first against the hull or superstructure of the target ship, where they detonated.  The major disadvantage was heavy fire from the target; low and fast meant there was no margin for error or mishap.  The early B-25s lacked sufficient forward firing armament to suppress enemy shipboard fire.  Later versions of nearly all Mitchells featured local modifications to increase the number of fixed forward firing .50 cal machine guns, controlled by the pilot and co-pilot, to as many as 12!

On 10 March 1944 the unit was moved to Exmouth Gulf in Western Australia in anticipation of a Japanese attack on the Australian mainland, which ultimatey did not eventuate. Squadron aircraft returned to Batchelor and resumed operations over Dutch New Guinea. From mid-1944 the number of Japanese fighters decreased and 18 Squadron aircraft began searching for prisoner-of-war camps across Java and dropping leaflets. Anti-shipping patrols continued and on 6 April 1945, in combination with Liberator bombers from 21 Squadron, 11 B-25s from 18 Squadron bombed the Japanese light cruiser Isuzu, which was evacuating troops from Timor. The damaged cruiser was sunk the next day by Allied submarines. Shortly after this success the squadron moved to Balikapan, Borneo,  to continue to drop leaflets, food, and medical supplies to prisoners held in Java, Borneo, and the Celebes.

No. 18 Squadron conducted more than nine hundred operational sorties during its wartime service, with ninety Dutch and twenty-five Australian personnel killed in action. Four thousand personnel from thirty-eight nationalities were posted to the unit over eight years. The Netherlands eventually took delivery of some two hundred forty nine B-25C, D and J variants – many were operated by 18 Sqn.

On 25 November 1945 the RAAF component of the squadron was disbanded.

Two months later the unit officially passed to Dutch control, flying against the Indonesian nationalists. Indonesian independence saw 18 Squadron handed over to the Indonesians and it was disbanded on 26 July 1950.


Compiled by Steve Larkins from a variety of sources including:

 AWM  - Unit Records  - To read more please click on Unit Records link to the right of this page (



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