How Did the Principles of Warfare Change Under the Daimyos

How did the principles of warfare change under the daimyos?

A) Heroic combat between champions remained the rule, but the weapon of choice changed from the bow to the curved sword.
B) Peasant forces were reduced in significance, as they were replaced by professional soldiers.
C) Scientific warfare based on spying, timely assaults, wise command and organization of massive armies replaced heroic combat.
D) The rise of gunpowder and cannon made the fortresses and castles of the warrior elite obsolete.