'Agas' was a series of Australian reconnaissance operations against the Japanese in Borneo by the 'Z' Special Unit (March/October 1945).

This undertaking supported Allied operations to secure North Borneo, and the closely related 'Semut' took place in Sarawak. Both operations combined and relayed their intelligence through the Stallion Project to Australian forces, and carried out guerrilla warfare against the Japanese in the region with support of the local population. A total of five 'Agas' operations was undertaken.

Early in the Pacific War, the Japanese had landed in north-western Borneo and quickly captured the area’s vital oilfields, which were restored to operability and started to benefit the Japanese war effort in 1943. Allied efforts to interdict the flow of oil had been limited largely to aerial bombing in the intervening period as Allied ground efforts had focused upon the drive to return to the Philippine islands group. Nevertheless, by a time late in 1944 and early 1945 the Allies had begun planning their Australian-led 'Oboe' operations to retake the area. The 'Oboe VI' operation to re-capture Labuan and Brunei Bay were scheduled for the middle of June 1945, and to support this, 'Agaswas launched in March 1945 by the Australian Services Reconnaissance Department utilising 'Z' Special Unit personnel. The operation had two main objects: the gathering of intelligence and tge training of indigenous people to undertake a guerrilla campaign against the Japanese. Subsequently, a series of five operations was undertaken in the Japanese-occupied areas of North Borneo in the final stages of the war within 'Agas' (the Malay word for sandfly). The Japanese forces occupying North Borneo at the time were drawn from Lieutenant General Masao Baba’s 37^th Army.

Planning for covert operations in Borneo by Allied forces had begun in December 1941 when 2^nd Lieutenant P. M. Synge, a British intelligence officer who had undertaken an expedition in Sarawak during 1932, proposed sending a small group of officers into the area to organise a guerrilla force with the aim of disrupting Japanese efforts to exploit the vital oilfields. Synge’s proposal was not implemented at the time, ands several other British officers made similar proposals. Throughout 1942 and 1943, British and Australian army planning staff worked to exchange information and sought out personnel who might be suitable. In October 1943 and January 1944, a reconnaissance operation was undertaken as 'Python' around Labian Point, Lahad Datu. Conducted in two phases, the operation was tasked with obtaining and relaying information about Japanese shipping and with supporting Filipino guerrillas who were working in the area under a US officer. Both phases were concluded without much success. Late in 1944 and early in 1945, the Allies began planning a campaign to retake Borneo, and as a result of the commitment of US forces to the recapture of the Philippine islands group, the task of recapturing Borneo was allocated primarily to Australian ground forces.

Early in March 1945, Major F. G. L. Chester, who had led the 'Python I' undertaking landed at Labuk Bay near Sandakan, along with six other personnel. Carried from Darwin aboard the US submarine Tuna, this 'Agas I' party had paddled 10 miles (16 km) ashore in inflatable rubber craft. Kayaks were then used to carry out reconnaissance in the smaller waterways along the shore of Labuk Bay. The party was able to establish a signals station at Lokopas and a hospital was established at Jambongan island for the guerrillas. Information such as the train schedule to and from Beaufort, cargo movements, and details of local timber milling and railway operations was collected. 'Agas I' also made contact with two Chinese men, Chin Sang and Ah Lee, who refused long-term co-operation with 'Agas I' men but were willing to provide the details of Japanese movements in the area. Information was also sought about Allied prisoners of war held at Sandakan, although the Australians were unable to get close enough to the camp to make a thorough investigation, and ultimately reported in error that the camp had been abandoned. In reality around 800 prisoners remained, and a planned rescue operation was cancelled as a result of the report.

Two months later the five-man 'Agas II' party led by Major R. G. P. N. Combe, landed at Paitan Bay near Sandakan, to obtain information in support of the planned 'Oboe VI' Australian assault on Brunei Bay and Labuan. Arriving by parachute in early May, the team established an intelligence network and undertook guerrilla activities at the Pitas, Kudat. Throughout the operation, the party was reinforced by nine more personnel and undertook a number of raids around Banggi island, Pitas, Maruda Bay, Dampirit and Pituru. Finally, in the closing stages of the war, Kudat was captured when the Japanese withdrew without resistance.

Starting on 21 June and again led by Chester, 'Agas III' focused its activities in the sector of Jesselton, Keningau and Beaufort. 'Agas III' was later incorporated into the Stallion Phase IV network, an intelligence-sharing network between Semut and Agas. The Stallion Phase IV project focused their reconnaissance on the Kimanis Bay area. In the middle of August, seven reinforcements were dropped by parachute on the Ranau plateau by the Royal Australian Air Force’s No. 200 Flight, to assist in locating prisoners of war who had escaped from Ranau camp. The 'Agas III' party remained in its area until withdrawn in the middle of October 1945.

Two more 'Agas' operations followed in July: 'Agas IV', consisting of three personnel under Major R. Blow, was landed by PT-boat in the Semporna area on 21 July, and was reinforced by some personnel from the North Borneo Armed Constabulary and the crew of a Royal Australian Navy whaleboat. Meanwhile, personnel from 'Agas V', under Major J. McLaren, landed around Lahad Datu on 27 July.

On 7 August, three 'Agas V' personnel and five local guerrillas moved to Talesai, to the north of Darvel Bay. 'Agas IV' was tasked with collecting information about Japanese troops in the Tawau, Mostyn and Lahad Datu area, ascertaining their strength, movements and combat capability. The party also undertook minor harassment attacks and worked to recruit local guerrillas, and continued operations until October 1945. 'Agas V' also gathered intelligence information, establishing and maintaining contact with several agents in their area, worked to establish hospitals and casualty collection points in the jungle, and worked to relieve food shortages in the area. The party ceased operations on 10 September 1945, and after this 'Agas V' personnel concentrated with the 'Agas IV' party around Semporna, where a Consolidated Catalina flying boat was to extract them.

Assisted by the 'Agas' and 'Semut' operations, Major General G. F. Wootten’s Australian 9^th Division was able to secure North Borneo, with major combat ending largely by July 1945. As the regular forces remained confined to the coastal areas, the Japanese moved inland and the irregular forces continued to play a role, calling in air attacks on the withdrawing Japanese and working to restore civil administration. After the end of hostilities, the Australian conventional troops remained in North Borneo to restore law and order, and to facilitate the surrender of Japanese troops. Extensive civic actions began even before the end of the war, with efforts being turned to rebuilding the oil facilities and other damaged infrastructure, establishing schools, providing medical care to local civilians and restoring the water supply. Martial law was initially imposed, but eventually a civil administration was established.

A total of 44 personnel took part in the 'Agas' operations. In overall terms, the 'Agas' operations were able to supply reliable information to the Australian conventional forces. The total estimated number of Japanese troops reported at 31,000 in May 1945 was far off the official number (35,000) given in October 1945. The 'Agas' operations also provided the crucial information that the Japanese in the area intended to evacuate the coast and move into the North Borneo interior.

Although 'Agas I' provided information about the 160-mile (260-km) 'Sandakan death marches' between January and March 1945, in which many Australians died, it did not execute any rescue missions. Nevertheless, it provided information that guided successful bombing raids at Sandakan. It also trained 250 people as part of the local guerrilla force, and more than 2,000 local inhabitants were able to receive treatment from the hospital set up by the party. The effectiveness of the 'Agas'-recruited guerrillas was limited, although around 100 Japanese were killed by these personnel.

'Agas II' also successfully set up a local guerrilla force of 150 to 250 people and contacted Chinese guerillas at Kota Belud. It also set up a hospital in the Lokopas area for the local population. Meanwhile, 'Agas III' proved largely unsuccessful. Many of its objectives were not met as a result of the high concentration in the area of Japanese troops, who numbered up to 6,000 men between Jesselton and Beaufort. The Chinese in this region also refused to provide any co-operation because of their fear of retaliation after the failed Jesselton Revolt in 1943. Nevertheless, intelligence gathered from this region enabled the Allies to avoid a direct assault against the Japanese during 'Oboe VI'.