According to some historians, French merchants from the Normandy cities of Dieppe and Rouen traded with the Gambia and Senegal coasts, and with the Ivory Coast and the Gold Coast, between 1364 and 1413. Probably as a result, an ivory-carving industry developed in Dieppe after 1364. These travels however were soon forgotten with the advent of the Hundred Years War in France. The states of the Wolof and Sereer, neighbouring the two colonial outposts, were particularly involved with the slave trade, having strong military organizations geared to supplying slaves to the Europeans.