Here it is replicated again;
You have misunderstood what i meant by sharing/adapting philosophical concepts from Buddhism (various schools) into warfare. As pointed out already warriors do not have the same goals as monks/nuns. Thus they do not have to seek sanction from Buddhist scriptures in order to adapt philosophical concepts to do their duties effectively. The specific philosophical concepts adapted from Buddhism are "Impermanence", "letting go of Self-Grasping", "Mindfulness", "No-Mind", "Immoveable mind" etc. Each of the above is a core philosophical concept directly relevant to the duty of a warrior. I already pointed to Jeffrey Mann's book if you want to know more on these. For a even more direct source see Takuan Soho's texts written to Yagyu Munenori on how to adapt Zen to Martial Arts translated by William Scott Wilson under the title "The Unfettered Mind" (https://en.wikipedia.org/wiki/The_Unfettered_Mind). Based on this Munenori wrote "Heiho Kadensho" which has also been translated by William Scott Wilson under the title "The Life-Giving Sword"(https://en.wikipedia.org/wiki/A_Hereditary_Book_on_the_Art_o...) These two are classic original source texts on the connection between Zen and Martial Arts.