to put an end to their custom of headhunting as well. During his tenure as Governor, Brooke's most well-known Dayak opponent was the military commander Rentap; Brooke led three expeditions against him and finally defeated him at the Battle of Sadok Hill. During the expeditions, Brooke employed numerous Dayak troops, quipping that "only Dayaks can kill Dayaks". Brooke became embroiled in controversy in 1851 when accusations against him of excessive usage of force against the Dayaks, under the guise of anti-piracy operations, ultimately led to the appointment of a Commission of Inquiry in Singapore in 1854. After an investigation, the Commission dismissed the charges. Brooke employed his Dayak troops during other military expeditions, such as those against the Chinese-Malaysian insurgent Liu Shan Bang and Sarawak warrior Sharif Masahor. After mass conversions to Christianity and anti-headhunting legislation by the European administrations was passed, the practice was banned and appeared to have disappeared. However, the Brooke-led Sarawak government, although banning unauthorized headhunting, allowed "ngayau" headhunting practices by the Brooke-supporting natives during military expeditions against rebellions throughout the state, thereby never really extinguishing the spirit of headhunting especially among the Iban natives. The state-sanctioned troops were allowed to take heads, properties like jars and brassware, burn houses and farms, exempted from paying door taxes, and in some cases, granted new territories to migrate into. This Brooke's practice was in remarkable contrast to the practice by the Dutch in the neighbouring West Kalimantan who prohibited any native participation in its punitive expeditions. Initially, James Brooke (the first Rajah of Sarawak) did engage his small navy in the Battle of against the Iban and Malay of the Saribas region and the Iban of Skrang under Rentap's charge but this resulted in the Public Inquiry by the colonial government in Singapore. Thereafter, the Brooke government gathered a local troop who were its allies. 20th century During the Second World War, Japanese forces occupied Borneo and treated all of the indigenous peoples poorly – massacres of the Malay and Dayak peoples were common, especially among the Dayaks of the Kapit Division. In response, the Dayaks formed a special force to assist the Allied forces. Eleven US airmen and a few dozen Australian special operatives trained a thousand Dayaks from the Kapit Division in guerrilla warfare. This army of tribesmen killed or captured some 1,500 Japanese soldiers and provided the Allies with vital intelligence about Japanese-held oil fields.