Final answer:
The English army's dominance in many battles during the Hundred Years' War was attributed to their use of the longbow and the establishment of trained, disciplined infantry armies.
Step-by-step explanation:
The two main advantages that helped the English army win many battles during the Hundred Years' War were their mastery of the longbow and the formation of disciplined infantry armies. The longbow was a powerful weapon that could send arrows farther and with more force than the French crossbows, which provided the English with a significant advantage in the early stages of the war. Additionally, instead of relying on feudal levies, the English kings began utilizing trained, disciplined infantry armies, which were more strategically flexible and effective than the traditional knight-based cavalry accustomed to feudal warfare. These professional soldiers were able to stand in compact formations, adapt to new military technologies, and were less reliant on the nobility's traditional martial role.