The Kamakura period (1192-1333) is important in Japanese history for two remarkable facts: the establishment of the government by the pioneer peasants and the emergence of religious sects for them. These two were the first in the world then.
As doctuments shows, in the Nara and Heian periods, you haven't found any trace of the peasants living and contributing to the governmetal system. They are thought to have been like slaves; I mean, they were allotted land and forced to grow crops for aristocracy.
In the second half of Heian period, some of the slaves ran away and pioneered into the Kanto area, called Bando then; there, they needed to protect their own land and lordship, so they began to carry arms with them. They are thought to have been the first Samurai (Japanese warrior).
A problem emerged then. The aristocrats in Kyoto, the former capital of Japan, tried to get them under their control, so they needed to protect their own land, followed by a war between Bando and Kyoto. The Bando won.
The leader of the peasants in Bando, Minamoto Yoritomo, took the soverinity from Mikado, the former name of Tenno or Emperor in Japanese (the word, emperor, cannot regarded as the exact word to translate "Mikado" into English; I will explain later) and opened the new government in Kamakura, the beginning of the Kamakura period, which you can call the second stage in Japanese history, the feudal system.
Through these events, the Bando peasants began to think about their own life. Every individual dies, but they try to survive. This contradictory movements in which persons are always must have been gazed at by them, and they needed to get a new kind of philosophy to see the world.
Then several Buddhistic sects were born, of which the two extreme sects were Jo-do Shinshu and Zen in the sense the former tells you to know your ignorance and impotence to upgrade you to a person with wisdom while the latter convinces you that your exaltation is the only way to give you the wisdom.
