Final answer:
The French secured victory in the Hundred Years' War through the decisive use of cannon and gunpowder, which dramatically changed siege warfare and rendered traditional defenses obsolete.
Step-by-step explanation:
By the end of the Hundred Years' War, the French gained victory because of e. cannon and gunpowder. The introduction of gunpowder weaponry transformed the nature of warfare, making the heavily armored cavalry and fortifications much less effective. Cannons and firearms allowed the French to breach the protective walls of castles and cities easier than before, drastically changing the tactics and outcomes of sieges. The use of gunpowder marked a shift towards more modern warfare and played a significant role in ending the long conflict in favor of the French, signaling the decline of traditional noble military units and ushering in an era where professional standing armies became the norm.