protect against raids from mountain tribes, who were known to engage in cannibalism. An expedition was launched against Bowu, an "influential cannibal chief". His village at Kaumumu was attacked and Bowu's severed head was displayed to the local people. However, "it is doubtful if the display of severed heads had the intended effect since these acts had taken place outside the customary ceremonial context". In 1921, the population of Bougainville was recorded at 46,832. The Australian district officer was based at Kieta and controlled a native police force of 40 constables and five officers. The civil administration "pursued pacification less ferociously than its military predecessor" and recruited Bougainvilleans as interpreters. The administration established larger "line villages" in place of the smaller hamlets, in order to simplify collection and "condition the able-bodied men to the barracks discipline on the plantations". German ethnographer Richard Thurnwald returned to Buin in 1933 following an earlier visit in 1908. He noted a number of changes over the 25-year period, including a large increase in literacy, the introduction of a cash economy (comprising both coins and shell money), the erosion of chiefly authority, a decrease in headhunting, and the introduction of feast-giving as a surrogate for war. The Australians had adopted many aspects of the previous German Administration. There was little difference between the two colonisers except for the expropriation policy and the line village consolidation program. The Germans had done the pioneering work in the colony and the Australians made this the foundation for colonial management. The 1920s saw the introduction of Protestantism to Bougainville, in the form of missionaries from the Methodist Church of New Zealand (1921) and the Seventh-day Adventist Church (1924). Tensions arose between the existing Catholic missionaries and the new arrivals, culminating in sectarian disturbances in Kieta in 1929. Father Albert Binois wrote to his superiors that the Protestants were "friends of the devil". The late 1920s and 1930s also produced an influx of anthropologists and ethnographers to Bougainville, among them Australians Ernest and Sarah Chinnery, Catholic priest Patrick O'Reilly, Briton Beatrice Blackwood, and American Douglas L. Oliver. Second World War In 1942, Bougainville was occupied by Japanese forces, who used it as a base to attack Guadalcanal and other Allied territory. In November 1943, the 3rd Marine Division landed on the west coast of Bougainville. Shortly afterwards the Battle of Empress Augusta Bay was fought between cruisers and destroyers of