The capture of Waruhiu Itote (nom de guerre ''"General China"'') on 15 January 1954 and the subsequent interrogation led to a better understanding of the Mau Mau command structure for the British. Operation Anvil opened on 24 April 1954, after weeks of planning by the army with the approval of the War Council. The operation effectively placed Nairobi under military siege. Nairobi's occupants were screened and the suspected Mau Mau supporters moved to detention camps. More than 80,000 members of the Kikuyu ethnic group were held in detention camps without trial, often subject to brutal treatment. The Home Guard formed the core of the government's strategy as it was composed of loyalist Africans, not foreign forces such as the British Army and King's African Rifles. By the end of the emergency, the Home Guard had killed 4,686 Mau Mau, amounting to 42% of the total insurgents.