As a result of the Allied bombing campaign against Nazi submarine bases during the Second World War, the cities of Brest, Lorient, and Saint Nazaire were nearly completely destroyed. Despite thousands of bombing missions, all three submarine bunkers still stand today. This monograph examines the effectiveness of the Allied bombing campaign against German submarine bases in Brittany by analyzing the campaign through the use of a design methodology. Research is broken down into three frames: the operational approach, the operational environment and the problem frame. The first frame provides an account of the bombing missions and effects. Next, an overview of the operational environment is conducted by exploring the historical context of Brittany, German construction efforts and Allied institutional barriers. The study concludes by examining the problem frame, which entails how the Allies perceived their operational problem and developed an approach based on their understanding. Ultimately, the Allies failed to accurately identify their problem and developed an ineffective approach towards defeating the threat. Had the Allies incorporated design thinking into their planning and execution, they may have developed an effective campaign towards defeating the Nazi U-boat threat rather than solving the wrong problem.