'The forgotten offensive' of the title is RAF Coastal Command's offensive against German sea trade between 1940 and 1945. RAF Coastal Command is more usually known for its anti-submarine campaign, but while engaged in these operations it was also making a true offensive against the enemy's merchant shipping in north-west European waters. Germany relied on foreign sources of supply for most of its vital raw materials, the most important of which was Swedish iron ore, which had to be brought by ship to Germany. Although Britain was aware of this weakness in German war-making capacity long before war broke out, RAF Coastal Command lacked the necessary equipment to attack it. This book argues that the preoccupation with strategic bombing doctrine was responsible for this lack, resulting in the effective exclusion of all other ideas on the employment of air power, including maritime and army support aviation. The fortunes of Coastal Command's campaign are followed throughout the war, demonstrating how lessons learned in the First World War had to be painfully relearned before the campaign became successful. Its success is then evaluated in terms of the volume of shipping sunk and, more importantly, the impact on the Germany economy. Among the important findings of this book is that Coastal Command's campaign should have been seen as a complementary strategy to the bomber offensive, the one cutting off vital raw materials and the other finishing the blow by directly assaulting enemy industry. Light is also shed on hitherto undiscovered aspects of British intelligence during the Second World War.