Z Special Unit (also known as Special Operations Executive (SOE), Special Operations Australia (SOA) or the Services Reconnaissance Department (SRD)) was a joint Allied special forces unit formed during the Second World War to operate behind Japanese lines in South East Asia. Predominantly Australian, Z Special Unit was a specialist reconnaissance and sabotage unit that included British, Dutch, Indian, New Zealand, Timorese and Indonesian members, predominantly operating on Borneo and the islands of the former Netherlands East Indies.[1]

The unit carried out a total of 81 covert operations in the South West Pacific theatre, with parties inserted by parachute or submarine to provide intelligence and conduct guerrilla warfare.[2] The best known of these missions were Operation Jaywick and Operation Rimau, both of which involved raids on Japanese shipping in Singapore Harbour; the latter of which resulted in the deaths of twenty-three commandos either in action or by execution after capture.

Operations Semut and Agas in North Borneo however were set the benchmark as far as successful intelligence gathering and guerrilla operations were concerned towards the end of the war in late 1944 onwards.

The Z Force implemented the Borneo Project in a series of long-term operations codenamed AGAS and SEMUT in North Borneo and Sarawak respectively. These SRD operations laid the groundwork to a certain extent, thereby paving the way for the eventual invasion in mid-1945 at the Brunei Bay-Labuan Island area. Basically, SRD operations focussed on two main objectives: the gathering of intelligence, and organizing (including training and arming) the local inhabitants into resistance groups to wage guerrilla warfare.

The operations prior to AGAS and SEMUT were PYTHON 1 and 2 carried out in North Borneo in the vicinity of Labuk Bay near Sandakan. PYTHON 1, led by Major F. G. L. Chester with landings in early October 1943, undertook the task of reporting on Japanese sea-traffic in the Sulu sea. Chester also provided support for Filipino guerrillas operating out of Zambonga.

In the later part of January 1944, PYTHON 2 began operations with the objective of organizing and training the native population for guerrilla warfare. These efforts do not appear to have been successful.

In May 1945, AGAS 2 led by Major R. G. P. N. Combe, the pre-war district officer of Kudat, landed at Paitan Bay. Combe focused almost entirely on building an intelligence network and trying to get some form of a guerrilla force up and running in the Pitas. AGAS 3, under Chester, focussed on the Jesselton-Keningau-Beaufort sector.

Meanwhile, in Sarawak, plans were in motion for a Z-Force team to be parachuted into the mountains of Sarawak with the objectives being the headwaters of the Baram, Limbang, and Trusan which would also include the Padas river area (Sapong, Beaufort, Tenom) including the rescue of downed allied airmen who were shot down in the vicinity of the area of operation.

SEMUT under the command of Major G. S. Carter saw the operation being divided into 3 areas of operation under 3 different commanders: SEMUT 1 under Major Tom Harrisson; SEMUT 2 to be led by Carter; and SEMUT 3 headed by Captain W. L. P.Sochon. The areas of operation were: SEMUT 1--the Trusan valley; SEMUT 2--the Baram valley; SEMUT 3--the entire Rejang valley with Bario being the insertion point for all SEMUT operations.

Harrisson and members of SEMUT 1 parachuted blindly into Bario in the Kelabit Highlands of the crocker range mountains in March 1945. Initially Harrisson established his base at Bario; then, in late May, shifted to Belawit in the Bawang valley (inside the former Dutch Borneo) upon the completion of an airstrip for light aircraft built entirely with native labour. In mid-April, Carter and his team (SEMUT 2) parachuted into Bario, by then securely an SRD base with full support of the Kelabit people. Shortly after their arrival, members of SEMUT 2 moved to the Baram valley and established themselves at Long Akah, the heartland of the Kenyahs. Carter also received assistance from the Kayans. Moving out from Carter's party in late May, Sochon led SEMUT 3 to Belaga in the Upper Rejang where he set up his base of operation. Kayans and Ibans supported and participated in SEMUT 3 operations. The nomadic Punans also extended a helping hand to Sochon and his comrades.

Prior to 10 June, D-Day of OBOE 6, Z Force units in North Borneo (AGAS) and northern Sarawak (SEMUT) were relaying gathering/collecting intelligence on Japanese troop strengths and movements in Borneo and sending valuable information to Morotai. . Z-Force units in Bario ( SEMUT) were successfully organizing, training, and arming native guerrilla forces and establishing Special Forces "A-teams" with a senior NCO's as team leaders (SEMUT Z-Force operators) and began to conduct clandestine operations in northern Sarawak. They also successfully established a small air strip for light aircraft to land and take off and safe air drop zones for supplies to be dropped from long range Liberator and Catalina aircraft of the US Navy.

In the mean time, Chester also conducted operations in the Papar, Beaufort, Mempakul, Menumbok, Spitang, Membakut and Kimanis bay area with the use of Catalina sea planes extracting natives for interrogation and information on Japanese troop movements and strengths, as well as advice on recommended landing/invasion locations in the bay of Brunei and Labuan.

AGAS 1 also began reporting back to HQ on the movement of prisoners of war from the Sandakan prison camp to Ranau and along the infamous death march route and establishing native and local "agents" and setting up radio communications all the way from Kota Belud to Kudat, to Pitas and to Labuk Bay but struggled to raise a sizeable guerrilla force owing to the fact the majority of chinese guerrillas refused to participate due to fear of reprisal after the failed Kwok rebellion in which hundreds were tortured and imprisoned with a sizeable number killed in Petagas and Labuan in October 1943.

With a reported Japanese troop strength of almost 35,000, it was common for trained guerilla's to desert the Z Force units to return to their villages for fear of Japanese reprisals against the native villages and family's, making AGAS a bit of a failure from an operational point of view.

Semut operators by now were already setting up medical facilities for the natives, and also establishing the routes Japanese forces generally used and also kept an eye on their movements. With a trained native force of well over 500 men, many armed with weapons and ammunition, and with the option to conduct offensive and defensive operations against the Japanese, natives were directed to deny Japanese forces food and supplies as much as possible. Japanese patrols sent in land to re-establish the food supply chain and/or to conduct interrogations of native villagers were consistently ambushed and wiped out.

Semut was so successful that well over 1000 Japanese troops were killed by their A-teams with head hunting expeditions during the Japanese retreat into Spitang and a series of ambushes resulting in minimal loss of life amongst the natives.

A similar head hunting expedition of anger was conducted by murut natives at the conclusion of the war against Japanese troops who had surrendered and were on their way from Keningau to Papar in late 1945 that resulted in heavy loss of lives amonst the generally unarmed Japanese troops.

Although the Z Force units were disbanded after the war, many of the training techniques and operational procedures employed were later used during the formation modern day Special Forces units around the world and remain a text book example for guerrilla operations and intelligence gathering.

Note: Much of the inspiration of the above comes from the work of Dr Ooi Keat Gin is associate professor in South-East Asian socioeconomic history and historiography at the School of Humanities, Universiti Sains Malaysia, in Penang, Malaysia. In his very detailed research, titled "Prelude to invasion: covert operations before the re-occupation of Northwest Borneo, 1944-45, Dr.Ooi touch's on many aspects of Z Force operations that are very detailed and in-depth, and something I have chosen not to do. He also discusses the reasons for the lack of support Chester faced from natives and chinese in modern day Sabah in conducting guerrilla warfare and also goes in extreme detail on the operations conducted by Tom Harrison and the other commanders of SEMUT in North Sarawak all the way down to Sibu.For further reading, please refer to the following link to his work:

http://www.thefreelibrary.com/Prelude+to+invasion%3a+covert+operations+before+the+re-occupation+of...-a0120109460

*The mention of the murut uprising against the Japanese forces after their surrender has been mentioned in three books that have been produced post-war although the number of murut warriors involved in the actual attacks and the number of Japanese troops killed in these attacks remains relatively unknown although it has been suggested by a Japanese commander the native force numbered 40-50 head hunters. Credit must be given to Dr.Danny Wong Tze Ken for bringing to my attention the sources of this information as it was his research that confirmed for me what I had known for many year's but was unable to prove with actual written fact and material.