The university is supposed to study everything but doesn't study the warrior spirit. This is one example of many, many low-hanging fruit that's simply being allowed to rot on the tree.
It's fine, I'll go. Let's start with the common knowledge.
The first part of the warrior spirit is called killer instinct. The single-minded focus on causing harm.
A person with killer instinct has a natural intuition for how best to cause pain, damage, and ultimately death. Vulnerabilities light up in space, strongly enough it's nearly a literal hallucination. They tend to naturally obey Machiavelli's dictum: do no small harm. [Proportional response] reads as some kind of foreign language. Once it's time to cause harm, they cause as much harm as possible, and forget that rules exist. There is no fair play or low blows, there is only victory or death. If the opponent doesn't fight back, then all the better; they will be killed efficiently.
Speaking of victory, the other part of the warrior spirit is the single-minded conviction of ultimate victory.
Once the warrior has homed in on the kill, they no longer consider attacks to be frightening, because they cannot result in defeat. They are merely obstacles. Yes, they must be bypassed, vaulted, or penetrated, but at the end of the day they are merely obstacles. You don't block a punch, you neutralize the punch's ability to ward off your own punches. No matter how inconvenient the path, the destination doesn't disappear. The warrior contemplates victory, becomes one with victory, and wins.
No warrior needs to read Sun Tzu, but he did say it correctly. When battle is joined, you should have already won. The battle is merely a question of how, exactly, you will win.
Someone without killer instinct forfeits victory. The warrior will kill their ability to fight while they hold back or flinch away from a harmful decision.
A person with killer instinct is a predator. They cannot help but see the weak as prey; the ability doesn't have an off button. And they're not wrong. And yes, victory is glorious or prey is delicious.
When there are indeed some rules that need to be respected, then the killer instinct makes it kinda difficult. It must be used to get victory, but it also must be contained. [To kill with restraint] sounds pretty stupid and it kind of is, but sometimes it must be done anyway. It's no good to win a battle but to lose a war, especially when that war can be won by refraining from action.
That said, why show mercy to someone who wishes to harm you? Defect on defectors, unless you're a masochist and want to be harmed again in the future. Praise Machiavelli and neutralize them utterly.
Once the fight is joined, there is no point contemplating defeat. If you thought there was any substantial chance of defeat, you ought to have surrendered rather than raised your arms. You already think you will win; believe yourself. Thoughts of defeat merely consume valuable brain cycles that could be used to strategize harm and execute said strategies.
What if you lose anyway? Then it sucks. The conviction of victory helps tremendously, converting many close shaves or outright losses into decisive owns. However, using it risks terrible backlash. Here and now is the time and place for a bit of Siddhartha: detach yourself. Get good at it so that, if you do lose, you can detach yourself after the fact rather than in the moment. The conviction has to be a slightly unreal conviction because all of your beliefs aren't quite real. They are things you hold, not things you are. Hold the conviction of victory because it works, but when it stops working, then let go of it. It's not [you] that's broken, merely that particular tool as applied to that particular conflict. The conviction of victory is a warrior thing, not a scholar thing; strictly speaking, it is in fact a delusion, and should never be taken wholly seriously.
If anyone wants to go beyond the common knowledge, they can talk about how, in training, defeat is preferable to victory.
For me, the warrior's weapon is the axe, not the sword.
The sword can do all sorts of fancy stuff to delight dancers and bards. It's not for fighting. The sword was a melee pistol. A sidearm for places fighting should not occur in the first place. Swords are, at least, prettier than pistols, and can (often should) be worn for decoration, like a fancy watch.
A battle axe is a brutal tool whose purpose is to kill a man. The son doesn't mourn his father less if you kill him impressively. Hack him with an axe and get it over with.
If someone is trying to hurt you, pull out the axe and down him like a tree before he can hurt you back. Glory to Victoria.