AIF troops were also dispatched from Darwin to the Netherlands East Indies (NEI) in the first weeks of the Pacific War. Reinforced battalions from the 23rd Brigade were sent to Koepang in West Timor ('Sparrow Force') and the island of Ambon ('Gull Force') to defend these strategic locations from Japanese attack. The 2/2nd Independent Company was also sent to Dili in Portuguese Timor in violation of Portugal's neutrality. The force at Ambon was defeated by the Japanese landing on 30 January, and surrendered on 3 February 1942. Over 300 Australian prisoners were subsequently killed by Japanese troops in a series of mass executions during February. While the force at Koepang was defeated after the Japanese landed there on 20 February and also surrendered, Australian commandos waged a guerrilla campaign against the Japanese in Portuguese Timor until February 1943. "Voyager" and were lost in September and December 1942, respectively, while operating in support of the commandos.