In April 1954, the British colonial government launched Operation Anvil, the largest security operation in the history of colonial Kenya. 25,000 soldiers and police sealed off Nairobi and conducted house-to-house searches, arresting every African man who could not prove they had a legitimate reason to be in the city. Over 30,000 Africans were detained in a single operation.
Families were separated. Workers were sent to detention camps. The operation was designed to eliminate Mau Mau support networks in the city.
It created a level of fear and humiliation that Nairobi's African communities would not forget for generations.