Ethos is a derivative of the same Greek word for ethics, and for the warrior comprises a code of conduct that guides his values and actions. It is often an oral code, passed down from one warrior to the next. Warrior ethos dictates not just how a warrior should behave towards his enemies, but also how he should relate to his people and overcome his own weaknesses. It is a philosophy that must balance the encouragement of active aggression with voluntary self-restraint. This tension lies at the core of warrior ethos.

https://www.thecollector.com/warrior-ethos-spartan-samurai-sioux/