On 15 February 1942, the British garrison at Singapore surrendered to the Japanese, in what Winston Churchill described as ‘the worst disaster and largest capitulation in British history’.1 The defeat dispelled the traditional view that Japan was a second-rate Oriental power, not possessing the military potential to challenge the West. For the following three and a half years, Britain struggled to regain its empire in the Far East, against an enemy whose fighting capabilities and will to resist surrender proved more resilient than ever believed possible. Intelligence enabled the British to understand their Japanese opponent, and played a crucial role in helping them develop the methods needed to conduct a successful war effort.