premise: Arromanches-les-Bains or simply Arromanches is a town in Normandy, France, located on the coast in the heart of the area where the Normandy landings took place on D-Day, on June 6, 1944.
hypothesis: Arromanches-les-Bains is where William the Conqueror planned his invasion of England.
reason: From the context, we do not know whether or not Arromanches-les-Bains is where William the Conqueror planned his invasion of England, therefore the statement is neither definitely correct nor definitely incorrect.