"China is the biggest [espionage] threat to the US today," David Szady, the US Federal Bureau of Investigation's (FBI) head of counterintelligence, told The Wall Street Journal on 10 August. It is a concern fuelled by a number of Chinese defectors in recent months who claim Beijing is engaged in large-scale intelligence-gathering operations overseas. Chen Yonglin, the first secretary of the Chinese Consulate General in Sydney, Australia, defected on 4 June. Chen told Australian authorities that Beijing had been overseeing a network of more than 1,000 spies and informers in Australia. These claims were mirrored in Canada in July when...