The priest Tannen used to say in his daily talks that:
A monk cannot fulfill the Buddhist Way if he does not manifest compassion without and persistently store up courage within. And if a warrior does not manifest courage on the outside and hold enough compassion within his heart to burst his chest, he cannot become a retainer. Therefore, the monk pursues courage with the warrior as his model, and the warrior pursues the compassion of the monk.
I traveled about for many years and met men of wisdom but never found the means to the pursuit of knowledge. Therefore, whenever I heard of a man of courage in one place or another, I would go and look for him regardless of the hardships on the way. I have learned clearly that these stories of the Way of the Samurai have been an aid on the road to Buddhism. Now a warrior with his armor will rush into the enemy camp, making that armor his strength. Do you suppose that a monk with a single rosary can dash into the midst of spears and long swords, armed with only meekness and compassion ? If he does not have great courage, he will do no dashing at all. As proof of this, the priest offering the incense at a great Buddhist memorial service may tremble, and this is because he has no courage.
Things like kicking a man back from the dead, or pulling all living creatures out of hell, are all matters of courage. Nevertheless, monks of recent times all entertain false ideas and desire to become laudably gentle; there are none who complete the Way. Furthermore, among warriors there are some cowards who advance Buddhism. These are regrettable matters. It is a great mistake for a young samurai to learn about Buddhism. The reason is that he will see things in two ways. A person who does not set himself in just one direction will be of no value at all. It is fine for retired old men to learn about Buddhism as a diversion, but if a warrior makes loyalty and filial piety one load, and courage and compassion another, and carries these twenty-four hours a day until his shoulders wear out, he will be a samurai.
In one's morning and evening worship, and as one goes about his day, he had best recite the name of his master. It is not a bit different from the Buddha's names and holy words. Furthermore, one should be in harmony with his family gods. These are matters of the strength of one's fate. Compassion is like a mother who nurtures one's fate. Examples of the ruin of merciless warriors who were brave alone are conspicuous in both past and present.
Yamamoto Tsunetomo, Hagakure, The Book of the Samurai, translated by William Scott Wilson.