Mau Mau Uprising attempt to eliminate Mau Mau's presence within Nairobi in one fell swoop. 25,000 members of British security forces under the control of General George Erskine were deployed as Nairobi was sealed off and underwent a sector-by-sector purge. All native Kenyans were taken to temporary barbed-wire enclosures, whereafter those who were not Kikuyu, Embu or Meru were released; those who were remained in detention for screening. Whilst the operation itself was conducted by Europeans, most suspected members of Mau Mau were picked out of groups of the Kikuyu-Embu-Meru detainees by a native Kenyan informer. Male suspects were then taken off for
Operation Anvil (Mau Mau Uprising) Mau" movement, had proliferated the Kikuyuland region. On 20 October the colonial governor declared a state of emergency, initiating efforts by the British military to put down the insurgency. The first months of the British campaign were plagued by a lack of discipline, communication, coherent strategy, and useful intelligence and little progress was made against the Mau Mau. An assault on the Naivasha police station and a massacre of civilians in the village of Lari in March 1953 dramatically escalated the conflict. Mau Mau activity also began to surface in the city of Nairobi, which had a large Kikuyu population.