After a spectacular victory in Malaysia, in the Indonesian archipelago and in the South Pacific after the attack on Pearl Harbor, the Japanese began the invasion of the island of Timor on February 20, 1942, which was then divided by two colonial powers, Holland in the West and Portugal in the East.
East Timor was considered a strategic point for the Japanese forces to stop a possible offensive from Australia, a few kilometers from the Portuguese colony.
The invasion of East Timor was made from Kupang and Dili, having met with a very strong resistance. On the island of Timor, there was the Sparrow Force which consisted mostly of soldiers from the Australian 2/40th Battalion and 2/2nd Independent Company. This force had been, cordially, displaced from West Timor (Dutch Timor) to the then Portuguese colony, although the Portuguese government has provided some objections.
The Japanese controlled both air and sea spaces, having at the end much of the 2/40th Australian Battalion surrendered. However, the 2/2nd Independent Company managed to escape and continued the fight, much thanks to the extraordinary assistance provided by the Timorese.
In addition to the provided assistance from the indigenous to the Australians in terms of food, shelter, transportation of heavy equipment and preparation of ambushes, the mountainous terrain of Timor also offered good conditions for the guerrillas, representing a clear advantage for Australian forces against the Japanese.
The existent Portuguese in East-Timor also provided some assistance to the guerrillas, in spite of, being Portugal a neutral country, these Portuguese had the right to maintain order in the colony.
On September 23, 1942, during unloading of supplies and evacuation of the wounded in Betano, the HMAS Voyager ran aground, and ended up being attacked by a Japanese plane. Being impossible to be towed, the Australians destroyed it completely to prevent the Japanese from capturing and using it.
Later, the 2/2nd Company was replaced by 2/4th Independent Company that ended up having a more remote relation with the Timorese population, since, in the meanwhile the Japanese had already been terrorizing them, forcing them not to provide assistance to Australians. The Japanese have also tried to make the Timorese from the western side of the East-Timor to convince the ones from the Portuguese side to stop helping the Australians. Furthermore, the Japanese tried deteriorate the relationship between the Timorese and Portuguese administration. In October, the control of the Portuguese had been virtually eliminated and in November the Japanese ordered the capture of all Portuguese present in the island.
The approximately 700 Australian commandos and the local population were eventually able to force the withdrawal of the 30,000 Japanese soldiers by the end of the year. During 1942, the Japanese had the following forces in the former Portuguese colony:
- 38th Infantry Division
- 48th Infantry Division
- 1st Infantry Regiment of Taiwan
- 2nd Infantry Regiment of Taiwan
- 47th Infantry Regiment
- 228 Infantry Regiment
- 1st, 2nd and 3rd Battalions of the 228th Infantry Regiment
- 1st Battalion of Artillery Mountain
At the end of World War II, 40,000 East Timorese were accounted as killed.