During the initial phase in early 1942, the Empire of Japan invaded the Australian-administered territories of the New Guinea Mandate (23 January) and Papua (8 March) and overran western New Guinea (beginning 29/30 March), which was a part of the Netherlands East Indies. During the second phase, lasting from late 1942 until the Japanese surrender, the Allies—consisting primarily of Australian and US forces—cleared the Japanese first from Papua, then the Mandate and finally from the Dutch colony. The campaign resulted in a crushing defeat and heavy losses for the Empire of Japan. As in most Pacific War campaigns, disease and starvation claimed more Japanese lives than enemy action. Most Japanese troops never even came into contact with Allied forces, and were instead simply cut off and subjected to an effective blockade by the US Navy. Garrisons were effectively besieged and denied shipments of food and medical supplies, and as a result, some claim that 97% of Japanese deaths in this campaign were from non-combat causes. According to John Laffin, the campaign "was arguably the most arduous fought by any Allied troops during World War II