While it may not have captured the modern imagination quite as much as The Battle of Britain, the Dambuster raids, D-Day and so on, the war waged against Briatin and its allies throughout the Second World War, came closest to inflicting defeat through starvation of food and also of fuel and materials. This talk begins by examining the origins of the Kriegsmarine's U-Boat arm, and its struggle to build up a warfighting strength against opposition within Germany. The talk will then look at rules of engagement in submarine warfare, and chart the rise of the U-Boat threat with early victories rising to a climax in mid-1943, after which the Allies began to master the threat. The talk examines strategies, tactics and the vessels and equipment used by each side, together with the role played by intelligence. It concludes with an assessment of the U-Boat campaign: its effectiveness, the value of measures and counter-measures, the statistics and overall results.