Asceticism often has a bad reputation in vitalist circles. The idea of the sexless, passionless, passive, world-rejecting monk seems self-evidently maladaptive, an evolutionary dead end, as Nietzsche and Savitri Devi surmised. Yet the fact is that monks have often been warriors, and the monarchs of ascetic religions, such as Christianity and Buddhism, have often been great conquerors. The Christian monastic orders contributed greatly to the fight against Muslim aggression in the Middle Ages and proved capable of exterminating the last pagan holdouts in the Baltic region.
In Japan, Zen Buddhism was the religion of the samurai, who developed a warrior ethos, Bushidō, which was one of the most profound and spiritual of its type in the entire world. Whereas Buddhism today is often associated with a kind of rootless, feel-good pacifism, in the first half of the twentieth century, the Zen schools of Imperial Japan enthusiastically supported national military power and selfless service to the Emperor as the divine embodiment of their nation. Zen monks and leaders developed a so-called “soldier-Zen” (gunjin-Zen) and strongly supported Japan during the Second World War, both in its imperial ambitions and in its resistance to the Allies. In the post-war years, many liberal Western converts to Zen were shocked to discover that their “enlightened” masters had supported authoritarian militarism and imperialism.
Personally, I have long thought that Zen spiritual practice could lead either to world-rejecting withdrawal or to detached, possibly violent, self-sacrifice of the kind evocatively described in the Hindus’ Bhagavad Gita. The Zen practitioner trains himself to tolerate discomfort, self-discipline, self-awareness, and ultimately a kind of transcendence of the self as illusory. One realizes, intimately, that one is nothing but a part of a boundlessly greater whole and a web of interdependent relationships. At the same time, there is a grim quality to Buddhism in general: Gautama’s insight was in recognizing the transience of all things: not merely of nations and empires and of one’s life and possessions, but even of one’s mind, even of the gods (on which the Nordic Eddur agree, for they foresee the inevitable Twilight of the Gods), perhaps even of the universe itself. In Zen in particular, all is “vacuity,” and one learns to stare into the void with serenity, without flinching, even cultivating a quiet, transcendent joy. However, not all are so strong. The “abyssal realization” can easily lead one to fall into despondent discouragement or withdrawn nihilism. There is little emphasis in Zen on building something that might outlive us, on the cultivation of Life.
Brian Zaizen Victoria, a Western Zen practitioner, has written a great deal on the now-politically incorrect attitudes of the Imperial Zen schools. In “A Buddhological Critique of ‘Soldier-Zen’ in Wartime Japan,”  Victoria provides an overview of soldier-Zen and translated extracts from its promoters (the quotes from Buddhist texts and Zen practitioners cited in this article are all drawn from Victoria’s chapter). Victoria argues that “soldier-Zen” was in fact non-Buddhist, claiming that Gautama himself was a preacher and practitioner of non-violence:
[W]hen looking at records of Buddha Śākyamuni’s life, we find his actions to be totally consistent with his earliest teachings. Śākyamuni peacefully sought to prevent war, as can be seen in his initial successful attempt to prevent an attack on his own country. Further, he successfully dissuaded King Ajātasattu from attacking the Vajjians. Still further, even when the very existence of his own homeland was at stake, he did not mobilize the members of the sangha as monk-soldiers to defend his country, nor did he use force to enlarge the power and landholdings of the sangha itself (as was later done in medieval Japan). 
However, Victoria recognizes that early on in the Mahayana tradition,  violence could be religiously sanctioned, which he claims were monastic rationalizations in the service of pro-Buddhist monarchs, and that such violence has been a recurring feature in Buddhist history. The first-century Nirvana Sutra had commanded “protecting the true Dharma [Buddha’s teaching] by grasping swords and other weapons.” In passing, it appears that the ancient Greek converts to Buddhism of Gandhara had, as monks and kings, a certain role in shaping and spreading Mahayana.
One can easily see how a belief in the transient unreality of the world could lead to an unsentimental attitude towards life. A seventh-century Chan (Chinese Buddhist) text, the Treatise on Absolute Contemplation, argued that killing is ethical if one recognizes that the victim is only empty and dream-like.  A millennium later, the seventeenth-century Zen master Takuan Sōhō wrote that:
The uplifted sword has no will of its own, it is all of emptiness. It is like a flash of lightning. The man who is about to be struck down is also of emptiness, and so is the one who wields the sword. None of them are possessed of a mind that has any substantiality. As each of them is of emptiness and has no “mind,” the striking man is not a man, the sword in his hands is not a sword, and the “I” who is about to be struck down is like the splitting of the spring breeze in a flash of lightning. 
The samurai appear to have had little difficulty in reconciling their Zen religion with their warrior ethos.
In the twentieth century, the Imperial Japanese developed soldier-Zen as a particular spiritual ethos compatible with their nation and state. This was advocated in particular by Lieutenant Colonel Sugimoto Gorō (1900-1937), who died in battle in China, and was honored by the Zen orders as a “military god” (gunshin).
Here are some passages from Sugimoto’s writings and sayings:
The Zen that I do . . . is soldier-Zen. The reason that Zen is important for soldiers is that all Japanese, especially soldiers, must live in the spirit of the unity of sovereign and subjects, eliminating their ego and getting rid of their self. It is exactly the awakening to the nothingness of Zen that is the fundamental spirit of the unity of sovereign and subjects. Through my practice of Zen I am able to get rid of my ego. In facilitating the accomplishment of this, Zen becomes, as it is, the true spirit of the Imperial military.
* * *
The emperor is identical with the Great [Sun] Goddess Amaterasu. He is the supreme and only God of the universe, the supreme sovereign of the universe. All of the many components [of a country] including such things as its laws and constitution, its religion, ethics, learning, art, etc. are expedient means by which to promote unity with the emperor. That is to say, the greatest mission of these components is to promote an awareness of the non-existence of the self and the absolute nature of the emperor. Because of the nonexistence of the self everything in the universe is a manifestation of the emperor . . . including even the insect chirping in the hedge, or the gentle spring breeze. . . .
* * *
If you wish to penetrate the true meaning of “Great Duty,” the first thing you should do is to embrace the teachings of Zen and discard self-attachment.
* * *
War is moral training for not only the individual but for the entire world. It consists of the extinction of self-seeking and the destruction of self-preservation. It is only those without self-attachment who are able to revere the emperor absolutely.
* * *
Life and death are identical. [Compare the Zen concept: “Unity of life and death” (shōji ichinyo)] . . . Warriors who sacrifice their lives for the emperor will not die, but live forever. Truly, they should be called gods and Buddhas for whom there is no life or death. . . . Where there is absolute loyalty there is no life or death. Where there is life and death there is no absolute loyalty. When a person talks of his view of life and death, that person has not yet become pure in heart. He has not yet abandoned body and mind. In pure loyalty there is no life or death. Simply live in pure loyalty!
* * *
In Buddhism, especially the Zen sect, there is repeated reference to the identity of body and mind. In order to realize this identity of the two it is necessary to undergo training with all one’s might and regardless of the sacrifice. Furthermore, the essence of the unity of body and mind is to be found in egolessness. Japan is a country where the Sovereign and the people are identical. When Imperial subjects meld themselves into one with the August Mind [of the emperor], their original countenance shines forth. The essence of the unity of the sovereign and the people is egolessness.
There is an almost “national-pagan” quality to soldier-Zen’s sublimation of the self into an assertive nation mystically united around a divine monarch.
Following his death in battle, Sugimoto was honored as a national hero by Yamazaki Ekijū, the head of the Rinzai Zen school. This is unsurprising given that Yamazaki’s Zen was firmly national and self-sacrificing. He said, “Japanese Buddhism must be centered on the emperor; for were it not, it would have no place in Japan, it would not be living Buddhism. Even Buddhism must conform to the national structure of Japan. The same holds true for Shakyamuni [Buddha]’s teachings.” He claimed that the Japanese had so cultivated selflessness that, “[f]or Japanese there is no such thing as sacrifice.” 
Yamazaki described Sugimoto’s death thus:
A grenade fragment hit him in the left shoulder. He seemed to have fallen down but then got up again. Although he was standing, one could not hear his commands. He was no longer able to issue commands with that husky voice of his. . . . Yet he was still standing, holding his sword in one hand as a prop. Both legs were slightly bent, and he was facing in an easterly direction [toward the imperial palace]. It appeared that he had saluted though his hand was now lowered to about the level of his mouth. The blood flowing from his mouth covered his watch.
In the past it was considered to be the true appearance of a Zen priest to pass away while doing zazen [seated meditation]. Those who were completely and thoroughly enlightened, however, . . . could die calmly in a standing position. . . . The reason this was possible was due to samādhi [concentration] power.
To the last second Sugimoto was a man whose speech and actions were at one with each other.
When he saluted and faced the east, there is no doubt that he also shouted, “May His Majesty, the emperor, live for 10,000 years!” [Tennō-heika Banzai]. It is for this reason that his was the radiant ending of an Imperial soldier. Not only that, but his excellent appearance should be a model for future generations of someone who lived in Zen. 
For Yamazaki, Sugimoto “demonstrated the action that derives from the unity of Zen and sword [zenken ichinyo].” Furthermore, “[t]hrough the awareness Sugimoto achieved in becoming one with death, there was, I think, nothing he couldn’t achieve.” 
Socrates is supposed to have said that all philosophy is a preparation for death. By that definition, there is no doubt that Zen is a true philosophy. The Soto Zen leader Ishihara Shummyō said:
Zen master Takuan taught that in essence Zen and Bushidō were one. . . . I believe that if one is called upon to die, one should not be the least bit agitated. On the contrary, one should be in a realm where something called “oneself ” does not intrude even slightly. Such a realm is no different from that derived from the practice of Zen. 
This sentiment is perfectly in accord with ancient Western philosophy’s attitude towards death, from Socrates to Marcus Aurelius.
I cannot say whether Mahatma Gandhi was right in claiming that all forms of violence are immoral. However, I observe that, in any case, the vast majority of mankind does not abjure violence. For most, then, the martial self-sacrifice of soldier-Zen cannot be bad in itself, but merely depends on the morality of the cause which it serves. Nor can I say whether Friedrich Nietzsche was right in claiming that the ascetic ideal is inherently emasculating and one needs a more primal, spontaneous, Dionysian way of life. However, we would have to admit that ascetic practices appear to have been central to the martial prowess of fighters as diverse as the ancient Spartans, the medieval Christian warrior-monks, and the Imperial Japanese. No doubt, different individuals will flourish and better actualize their potential in following a more ascetic or more “barbaric” ethos, depending on their temperament.
After the Second World War, the Americans demanded that the Japanese Emperor renounce his claims of godhood. This may have been understandable from a rationalist and materialist liberal perspective, which saw these claims as not only self-evidently false and even deceitful, but also as having provided part of the foundation for Japanese militarism and international aggression. But there was also a price to be paid: the disenchantment of Japan, the reduction of that nation from a mystical family with a special destiny to a mere population of consumers. Human life, no doubt, suffers and becomes impoverished from a lack of a sense of higher purpose. I will not bore you by citing the various psychological studies suggesting this. Each one who, with but a little sensitivity, looks into his own heart will know it to be true.
I do not accept that nothing exists besides this transient world and that, therefore, nothing in a sense ultimately exists. Even when the Himalayas are ground to dust, humanity goes extinct, and this universe itself is torn asunder, some things, I can sense, will always remain and are eternal: the principles of reason and the yearning-for-life. Individual human life, in all its arbitrariness and brevity, seems to have meaning only if that existence can truly be recognized and lived as part of a greater whole. That was evidently one of the ambitions of soldier-Zen.
  Brian Zaizen Victoria, “A Buddhological Critique of ‘Soldier-Zen’ in Wartime Japan,” in Michael Jerryson & Mark Juergensmeyer (eds.), Buddhist Warfare (Oxford: Oxford University Press, 2010), pp. 105-30.
  Ibid., p. 126.
 Mahayana, or the “Great Vehicle,” refers to the great branch of Buddhism largely coterminous with the East Asian nations. It is often contrasted with Theravada Buddhism, which is often criticized by Mahayana Buddhists as aiming for a “nirvana” which means non-existence or oblivion.
  Ibid., p. 123.
  Ibid., p. 118.
  Ibid., p. 111.
  Ibid., p. 115.
  Ibid., p. 114.
  Ibid., p. 119.