The first reason is that King Phillip VI tried to seize the English territories in the duchy of Aquitaine. England tried to take the French throne. The second reason is that because of their historical feudal orders, France and England broke away from one another (Allmand 7). The third reason was The Battle for Flanders. Flanders was the industrial center of northern Europe. It had become very prosperous through its cloth manufacture. To satisfy its market, it needed more wool. So they imported fine fleece from England. England depended upon this trade for its foreign exchange. The upper-class English had adopted Norman fashions and switched from beer to wine during the 1200s.
Note that beer and wine were very important elements in the medieval diet. Both contain vitamin and yeast complexes that the medieval diet, especially during the winter, did not provide. Besides, the preservation of food was a difficult matter in that era, and the alcohol in beer and wine represented a large number of calories stored in an inexpensive and effective fashion. People did get drunk during the middle ages, but most could not afford to do so. Beer and wine were valued as food sources and were priced accordingly (Lynn Harry Nelson, The Hundred Years' War 1336-1565)
England had a dilemma. They could not grow grapes to manufacture the wine that many of the English now wanted. So, they had to import it. A triangular trade took place. In this trade, English fleece was exchanged for Flemish cloth. The Flemish cloth was traded with southern France and exchanged for wine. The wine was then shipped into England and Ireland (Allmand 40)
The French attempted to get back control of the region in order to manage its riches. The English could not allow this because it would suggest that the French ruler would have control over their