In the interests of national security, my luggage was recently searched at Los Angeles airport. The culprit: Spy Catchers. The uncorrected proof copy was so bulky that it triggered an alert. I declined to tell the Customs and Border Protection officer (in no mood for irony) that one chapter in the offending item was entitled ‘Keeping out Undesirables’. David Horner’s first volume in the history of ASIO is a big book – big on detail, broad in scope, and, overall, impressive in achievement.

The original raison d’être of ASIO was to catch spies, hence the book’s title. It is now common knowledge that Prime Minister Ben Chifley established ASIO not to combat domestic communism but to satisfy American and British security concerns. This was after the ultra-secret Venona decrypts revealed the existence of a Soviet spy ring, the ‘Klod’ network, operating in Australia. Indeed, much of this story has already been told by Horner and Des Ball in Breaking the Codes: Australia’s KGB Network, 1944–1950 (1998). But ASIO’s counter-espionage function was soon joined by a counter-subversion function. Targeted were the Communist Party of Australia (CPA), front organisations, and fellow travellers. Examining and evaluating how ASIO fulfilled these dual roles, which frequently overtaxed the resources and expertise of the young security service, forms the core of Horner’s narrative.