From the archives of Zumdol Tamun, practitioner and scholar of armed and unarmed combat:
There are many different concepts that define, collectively, the nature of combat in all its forms. There are essential fundamental elements, broad facets and contexts, principles and techniques for various overlapping contexts.
I will first list certain principles I deem minutiae. These are concepts that present certain principles useful for specific contexts, as well as concepts that simply highlight potential options, along with their pros and cons.
Rith Asmur (The Weak Grasp):
An armed opponent is a more confident for and potentially a greater hazard, whether you are armed or unarmed. For this reason, it is common to prioritize disarming over incapacitating such a foe. However, these goals are not mutually exclusive.
Consider the limb holding an opponent's weapon. Any disabling strike to said limb can potentially disarm the foe, but such a strike must be applied correctly. The shoulder and elbow are tempting targets, easier to hit than the hand itself, but a wound there is less likely to be definitive. You do not want a gladiator's wound, a slash into the shoulder that gives a deceptively bloody appearance while serving no purpose.
A strike to the hand itself, or even the fingers, directs force against a more vulnerable target, and even if it fails to disarm the foe it may incapacitate the target anyway. This allows techniques to potentially disarm and/or incapacitate in the same action, making the technique more efficient via more potentially favorable outcomes.
Ramac Duto (The Lizard's Tail):
This covers a principle that is useful to exploit when it occurs, but is not deliberately exploitable barring risk of death.
Combat always entails some risk to life and limb, and the latter inspires great dread in any reasonable being. Wounds may heal and bones may mend, but to lose a limb is to be made unwhole. However, it is not always an outcome to be feared.
A savage foe may seek to rend flesh with a wicked bite. Or a foe might direct a solid strike to a vulnerable target. If a grave wound is inflicted that shatters the bone, you may be rendered at the mercy of your foe. But the body is adept at handling certain forms of shock, and it is possible to fight on even after a clean amputation. Should you answer this injury with a more decisive strike, you may well live to fight again.
This is especially useful when stricken by a fearsome beast. Should a foe's jaws find their mark, it is natural instinct to follow through with an effort to savage the victim further, and make the injury more grievous. This can have deadly consequences.
Uzin Usan (The Iron Heart):
A skilled combatant may notice signs of a fatal blow, of strikes that will lead to death even if they are not immediately incapacitating. But senses can deceive, especially when the observer is the would-be victim.
A solid blow to the heart of lungs has certain effects on the body, presenting signs that you may interpret as a mortal wound. But most can live on even with injuries that are effectively bruises, and even a truly severe blow to the lung is not as dire as it might feel. If you received a strike that did not mar your flesh, do not yet resign yourself to fate.
Kose Ozi (The Swift Arm):
Most students of martial arts are concerned with close combat, whether armed or unarmed. To strike at range is given little thought, or sometimes treated as outside the scope of their training. But in this case I will demonstrate a concept proving this false.
Before contact is made and your full range of experience can serve you, a confrontation may start such that ranged weapons are an option. But to loose an arrow or bolt presents a moment of vulnerability, which may be exploited if your shot fails to incapacitate the foe.
Casting missiles at the enemy by hand is sometimes looked down upon by those experienced in archery, but there are contexts in which this is the superior option. The body readies itself faster, with movement swift and sure. It is instinctive, whereas archery relies on learned motion.
Nemen Jathrur (The Righteous Hawk):
There are foes, both man and beast, that do not succumb to single decisive blow. Whether you seek to incapacitate or kill them, they may prove impossible to defeat without repeated wounds and constant risk. But there are ways to neutralize a foe without even incapacitating them, and they can be made as decisively as a killing blow against a mundane foe.
To strike the lungs can deal a mortal blow, but it is also debilitating in its own way. An opponent straining to breathe is unable to act and react as swiftly and surely.
Injury of the bowels can hinder any creature susceptible to a low blow of that sort, and nearly any being that partakes of food is susceptible. If the injury is at least of moderate severity, the creature's reaction shall delay and distract them.
If your foe has a head or anything akin to it, there remains an option even if head wounds prove indecisive. With any life of such complexity, the mind and body are linked in a manner that can be exploited. A solid blow to the neck or farther down the spine can still prove useful.
Lastly, no matter how many limbs a creature may stand on, being grounded is a severe detriment to their ability to fight. This is the literal and metaphorical foundation of such a creature's method of combat, and removing it limits their options.
Nońi Thil (The Lost Sword):
If you are armed, you may see yourself as having an advantage. The wise combatant already knows to use all weapons available to them, natural or otherwise. But even those wise ones may forget to use a given weapon to its fullest extent.
A wise swordsman may see fit to cut, thrust, or both as the situation warrants. But they may fail to use techniques relying on the pommel or the flat of the blade, and miss the rare instances when doing so is superior to their favored methods.
But it isn't merely a matter of opportunity. Efficiency is key to using your options to their fullest. You may notice a moment where a little-used technique will land with greater certainty, but how likely will it have a desirable effect? Exploiting attacks of opportunity require balance between the action and the result.
Honu Asi (The Blunt Spear):
There are instances where the little-used techniques are not only useful, but superior or even the only viable option. Consider a hardened foe, one that may even be invulnerable against your best techniques. but you may discover a single method that has some useful effect.
If surrender or flight is not an option, all that remains is to use what works, either until your options change or until one of you is victorious.
If a beast of bronze withstands a copper spear, but a strike with the shaft marks its form, then the strong shall yield to the weak, if the weak can but persevere.