Japan summaryduring the time of the 'Three Great Unifiers" in Japan, what would be a good summary for (why Japan finally developed a centrilized regime after centuries of feudalism?)
I'd say that it was a combination of military leadership and the fact that Japan was tired of the chaos that they had been experiencing.
Oda, Toyotomi, and Tokugawa were all obviously very skilled military leaders, which helped them consolidate power. But they were also able to convince the daimyo to give up their claims to power and united under (eventually) the Tokugawa shogunate. I think this happened mainly because the chaos had not really been good for anyone in Japan and so the daimyo were ready for a change.
My guess is that the decline of feudalism in Japan had little to do with the major players being war-weary and consensus was achieved by some volunteering to step down from political power. It seems the case historically that this never happens; Centralization occurs because power is consolidated and then the one stronger entity either subsumes or destroys the weaker entities.
There was a real sense of war fatigue at the time. Let us remember that centuries of feudalism had resulted in much hardship and suffering across Japan as rival warlords attacked each other and tried to expand their own territory. Centralisation of power acted as a necessary antidote to this instability and chaos.