The International Force East Timor (INTERFET) was a multinational non-United Nations peacemaking task force, organised and led by Australia in accordance with United Nations resolutions to address the humanitarian and security crisis that took place in East Timor from 1999–2000 until the arrival of UN peacekeepers. INTERFET was commanded by an Australian military officer, Major General Peter Cosgrove.

Background Indonesia invaded East Timor in 1975 and annexed the former Portuguese colony. The East Timorese resistance movement Falintil resisted the annexation. The annexation by Indonesia was not recognised by the United Nations, but was recognised by one state, Australia, in 1979. Cold War security concerns were emphasised, while foreign powers also placed high importance on good relations with Indonesia and were largely reluctant to assist a push for independence as a result. However, following the fall of long-serving Indonesian President Suharto, the new president, B. J. Habibie, was prepared to grant East Timor special autonomy.

In late 1998, the Australian prime minister, John Howard, with his foreign minister, Alexander Downer, drafted a letter to Habibie supporting the idea of autonomy but incorporating a suggestion that the long-term issue of East Timorese self-determination could best be defused by providing the East Timorese with an opportunity for a plebiscite after a substantial period of autonomy. The explicit comparison was with the Matignon Accords involving France and New Caledonia. The letter upset Habibie, who saw it as implying Indonesia was a "colonial power", and he decided in response to announce a snap referendum to be conducted within six months.

News of the proposal provoked a violent reaction from pro-Indonesian militia in East Timor. The Indonesian army did not intervene to restore order. At a summit in Bali, Howard told Habibie that a United Nations peacekeeping force should oversee the process. Habibie rejected the proposal, believing it would have insulted the Indonesian military.

East Timorese independence referendum

The United Nations Mission in East Timor (UNAMET) was established to organise and conduct a referendum on the question of independence. It was composed of police and observers rather than military personnel. The UN-sponsored referendum held on 30 August 1999 showed overwhelming approval for East Timorese independence from Indonesia. After the result was announced on 4 September, violent clashes, instigated by a suspected anti-independence militia, sparked a humanitarian and security crisis in the region, with Xanana Gusmão calling for a UN peacekeeping force the same day. Many East Timorese were killed, with as many as 500,000 displaced and around half fleeing the territory.

On 6 September, Operation Spitfire commenced with Royal Australian Air Force (RAAF) C-130 Hercules aircraft evacuating UNAMET staff, foreign nationals and refugees, including Bishop Belo, to Darwin from Dili and Baucau airfields with protection provided by unarmed Special Air Service Regiment (SASR) soldiers.

United Nations resolution The violence was met with widespread public anger in Australia, Portugal and elsewhere, and activists in Portugal, Australia, the United States and other nations pressured their governments to take action. Australia's Opposition Spokesman on Foreign Affairs, Laurie Brereton, was vocal in highlighting evidence of the Indonesian military's involvement in pro-integrationist violence and advocated United Nations peacekeeping to support the East Timor's ballot. The Catholic Church in Australia urged the Australian Government to send an armed peacekeeping force to East Timor to end the violence. Protests occurred outside the Indonesia Consulate in Darwin and the Indonesian Embassy in Canberra.

The Australian prime minister, John Howard, gained the support of United Nations Secretary-General Kofi Annan and U.S. President Bill Clinton for an Australian-led international peacekeeping force to enter East Timor to end the violence. On 12 September, Clinton announced:

Indonesia, in dire economic straits, relented. Under international pressure to allow an international peacekeeping force, President B.J. Habibie announced on 12 September that he would do so. He told a press conference:

On 15 September 1999, the United Nations Security Council expressed concern at the deteriorating situation in East Timor and issued its Resolution 1264 calling for a multinational force to restore peace and security to East Timor, to protect and support the United Nations mission there, and to facilitate humanitarian assistance operations until such time as a United Nations peacekeeping force could be approved and deployed in the area. The resolution also welcomed Australia's letter to accept the leadership of a proposed multinational force in East Timor and to make a substantial contribution to the force itself.

Military operations The lead-up to the operation remained politically and militarily tense. The Royal Australian Air Force (RAAF) re-deployed frontline combat aircraft—F/A-18s and F-111s—northward to Tindal in the Northern Territory to act as a deterrent against escalation of the conflict by the Indonesian military and provide close air support and air defence in support of the landing if required. P-3C Orion maritime patrol aircraft were also deployed. At peak strength the RAAF aerial support assets available to INTERFET included 10 F-111s, 12 F/A-18s, five P-3C Orions, three B707 aerial refuelling tankers, two B200 King Airs, three PC-9A forward control aircraft, and a Falcon F900 VIP jet. Also in support was a significant airlift group, with Australian transport aircraft including thirteen C-130 Hercules and three DHC-4 Caribou. New Zealand deployed C-130 Hercules, Bell UH-1H Hueys, and A-4K Skyhawks to RAAF Base Tindal to support RAAF F-111s. In addition, a number of British, United States, Canadian, French and Thai aircraft were also deployed. On at least one occasion Australian P-3C aircraft were intercepted by Indonesian aircraft, while an Indonesian submarine was also detected by Coalition surveillance within the vicinity of Dili Harbour as INTERFET forces approached. Ultimately no serious incidents occurred and the intervention was successful; however, Australia–Indonesia relations would take several years to recover.

Of the 22 nations involved in INTERFET, 10 provided naval assets. Australia was the single largest provider, with 14 ships deployed with INTERFET between 19 September 1999 and 23 February 2000: the frigates , , , , , and ; the landing ship , the landing craft , , , , and ; the fast transport ; and the replenishment vessel . The United States contributed seven ships: the cruiser ; the amphibious assault ships , , and ; and the replenishment ships , , and . France supplied four vessels: the frigates Vendémiaire and Prairial plus the landing ships Siroco and Jacques Cartier. Singapore contributed the amphibious landing ships Excellence, Intrepid, and Perseverance. New Zealand deployed the frigates and and the replenishment ship . Other naval vessels deployed during the operation included the Canadian replenishment ship , the Italian amphibious assault ship San Giusto, the Portuguese frigate Vasco da Gama, the Thai landing ship Surin, and the British destroyer .

The International Forces East Timor (INTERFET) coalition began deploying to East Timor on 20 September 1999, as a non-UN force operating in accordance with UN Resolutions. Led by Australia, who contributed 5,500 personnel and the force commander, Major General Peter Cosgrove, it was tasked with restoring peace and security, protecting and supporting UNAMET, and facilitating humanitarian assistance. Commander of the Thai Task Force Major General Sonkitti Jaggabattra was INTERFET's deputy commander. The Australian Deployable Joint Force Headquarters provided overall command and control. The main Australian combat element included infantry and cavalry provided by the 3rd Brigade. Due to the nature of the operation the force deployed without its artillery and other heavy weapons and equipment; however, 105 mm and 155 mm guns and Leopard tanks were available and on standby in Darwin for rapid deployment if required. It was supported by the 3rd Combat Engineer Regiment, 103rd Signals Squadron, 110th Signals Squadron, and elements of the 3rd Brigade Administrative Support Battalion. Twelve Black Hawk helicopters from the 5th Aviation Regiment were also deployed. Other force level troops included military police, an intelligence company, an electronic warfare squadron, elements of an artillery locating battery, and topographic survey personnel.

Special forces played a key role, with an Australian squadron from the Special Air Service Regiment (SASR), a troop from the New Zealand Special Air Service (NZSAS) and a troop from the British Special Boat Service (SBS) forming Response Force (RESPFOR). The SASR flew into Dili by RAAF C-130H Hercules securing Komoro Airport followed by NZSAS and SBS. With the airhead secured, infantry from the 2nd Battalion, Royal Australian Regiment (2 RAR) then flew in from Darwin supported by two M-113 armoured personnel carriers from B Squadron, 3rd/4th Cavalry Regiment. RESPFOR began vehicle patrols into Dili, including reconnaissance of Dili port, after which a rifle company from 2 RAR—borrowing Indonesian military trucks for transport—secured the port prior to the arrival of follow-on forces the next day, while the remainder of the battalion consolidated the position at Komoro. Meanwhile, an advance party of Gurkhas from the 2nd Battalion, The Royal Gurkha Rifles (2 RGR) and British Royal Marines Commandos from the Fleet Standby Rifle Troop (FSRT) secured the foothills and areas to the south of the city. 3rd Battalion, Royal Australian Regiment (3 RAR) began landing the next day at the port, along with the 2nd Cavalry Regiment equipped with ASLAV light armoured vehicles and the remainder of the Company Group from 2 RGR arrived. No. 2 Airfield Defence Squadron (2AFDS) arrived the following day to permanently secure Komoro airport replacing 2 RAR. Additional Australian forces and support personnel arrived in the days that followed as INTERFET continued to grow, as did forces from a number of other countries, in particular from New Zealand.

Most United Nations Mission in East Timor (UNAMET) personnel had already been evacuated from the region in the preceding months by the Royal Australian Air Force, although a small number had remained behind. With the withdrawal of the Indonesian forces and officials, UNAMET re-established its headquarters in Dili on 28 September and on 19 October 1999, Indonesia formally recognised the result of the independence referendum. Soon after, the United Nations Transitional Administration in East Timor (UNTAET) was established as a peacekeeping operation which was also fully responsible for the administration of East Timor to oversee its transition to independence. With only limited forces available, Cosgrove adopted the 'oil spot' concept of dominating key areas from which the surrounding areas could be influenced and then secured, moving quickly by helicopter to keep the militia off balance. The large airfield at Baucau was secured by two platoons from 2 RAR on 22 September, who were relieved by the Philippine Army non-combat contingent known as the Philippine Humanitarian Support Mission to East Timor (PhilHSMET) three days later.