On the Samurai-Archives Online Citadel, the hot topic is the ashigaru. I do know this. Around the very early 1570s, Nobunaga's army was almost made up of full-time soldiers. This is important. Where as other warlords did not have the luxury to fight on a day in and day out basis. The word I found to suit this is HeinouBunri. The separation of warrior farmer. His full-time army allowed him gobble up other domains and quickly consume power. Nobunaga started it and then Hideyoshi took over.
Nobunaga no Tame!