In 1900, a handful of New Zealand police detectives watched out for spies, seditionists and others who might pose a threat to state and society. The Police Force remained the primary instrument of such human intelligence in New Zealand until 1956 when, a decade into the Cold War, a dedicated Security Service was created. Over the same period, New Zealand' s role within signals intelligence networks evolved from the Imperial Wireless Chain to the UKUSA intelligence alliance (now known as Five Eyes).The first of two volumes chronicling the history of state surveillance in New Zealand, Secret History opens up the ' secret world' of security intelligence through to 1956. It is the story of the surveillers who ? in times of war and peace, turmoil and tranquillity ? monitored and analysed perceived threats to national interests. It is also the story of the surveilled: those whose association with organisations and movements led to their public and private lives being documented in secret files.Secret History explores a hidden and intriguing dimension of New Zealand history, one which sits uneasily with cherished national notions of an exceptionally fair and open society.