Operation Sealion: Simulating the naval component of a 1940 German invasion of Britain

In this thesis, we will study the naval component of Operation Sealion, the proposed 1940 German invasion of Britain. This never happened as during the Battle of Britain, the Luftwaffe did not achieve the level of air superiority required for the invasion to start. We aim to answer the question of whether the Germans could have gotten a sufficient force ashore. We developed two counterfactual scenarios, a 2-sigma scenario and a 6-sigma scenario, where the Luftwaffe win the Battle of Britain by a small and large margin, respectively. We used these counterfactuals to wargame the final German preparations, such as the laying of minefields. In the 6-SD wargame, the Germans were able to lay approximately 75% of their planned minefields, but only 20% in the 2-SD wargame. We then developed a simulation of the initial three days of Operation Sealion, where around 120,000 German troops would be shipped across the Channel using barges and transports, with the Royal Navy attempting to sink them. During each run of the simulation, parameters such as the effectiveness of British destroyers against barges were chosen from a prior distribution, allowing us to estimate dependencies between different quantities. We discovered that the most critical factor in Operation Sealion was the effectiveness of minefields. We found that if the outcome of the Battle of Britain was similar to reality or even slightly in favour of the Luftwaffe, as in the 2-SD simulation, then the Germans would not be able to get a sufficient force ashore, hence the invasion would be unsuccessful. However, if the Luftwaffe had won the Battle of Britain by a very large margin, as in the 6-SD simulation, then the Germans could have gotten a large army ashore, potentially paving the way for a successful invasion.