In 1757, Cesar-François Cassini de Thury (1714–84) published a map of the region north of Abbeville as part of his family's multigenerational atlas of France (Carte générale de la France, No. 4, feuille 12; see Figure 1, below). Cassini's rightfully famous map is a fascinating, detailed look at that country in the mid-eighteenth-century: roads and towns, windmills and shrines, drainages, and even the small tracks through the nearby Forest of

Crécy all appear to be remarkably accurate to what modern surveyors can map on the ground. And clearly marked upon it, in the Vallée des Clercs beside a small hill rising to the northwest over and immediately adjacent to the town of Crécy-en-Ponthieu, is the location of the Battle of Crécy on 26 August 1346. Cassini's map is, insofar as I am aware, the first definitive identification of the specific site of the Battle of Crécy. It established (or at least memorialized) what is now considered the traditional battlefield, and that location has stood almost entirely unquestioned for over 250 years. One of the few exceptions occurred in 1845, when Joachim Ambert suggested, based on Froissart's report of a location between Crécy and “Labroie” (Items 76.287, 81.433), that the battle instead occurred just north of the village of Estrées-lès-Crécy, where the Chaussée Brunehaut now runs across open fields. As Philip Preston has rightly observed, however, Ambert's suggestion “is unconvincing and has had no impact on subsequent writing on the battle.” In the many years since Ambert's work, I know of no other book referencing the battle, no interpretation of this great event, no published report, that has called for an alternative location — and almost all have simply accepted the traditional site, usually without the slightest hint of concern or question.

As might be expected given this preamble, it is my contention that Cassini, like Ambert, got it wrong, and that every subsequent interpreter has of necessity misunderstood one of the most famous battles of the Middle Ages: without understanding the land, one can hardly understand the action. After all, Cassini's error, as we shall see, was no small one. The Battle of Crécy happened not upon the hill he claimed but upon another, 5.5 km to the south.