Imagine a war in a standard fantasy world, roughly medieval, most magic is limited, but magical healing exists. Healing comes in three forms:
Rare Healers, who are born with ability to do rapid magical healing, taking even severely injured to full health in minutes. However, they exhaust their own Healing energies rapidly doing so, and thus can only heal a few wounded this way before exhausting themselves entirely. These are far rarer than trained medics, but not unheard of, and a number will be available to each side in a battle.
If a Healer exhausts his energy, it can take a few days to fully recover. It is easier for a Healer to heal recent wounds then old ones, though having time to focus on Healing without rushing, and ability to triage who to Heal better, means that they can heal a slightly more effectively if not in the heat of battle even if the wounds are a little older. After a battle, once healers recover their expended energies, they will work to heal those wounded from previous battles, but since the wounds are now much older, they can not heal these older wounded nearly as fast.
Alchemical potions that can be used for healing. These potions are usually not as rapid, but can heal someone back to fighting strength in between a a number of hours to a few days depending on injuries and potions used. Alchemy is more than "
ydamage". It takes trained Medics to know how to use these potions well, combining them correctly for different injuries; and more potions doesn't necessarily mean faster healing. These resources are more far more common then Healers, but still limited in supply and carefully triaged.
General first aid and 'mundane' healing, supported slightly by some simpler magic, mostly to lower odds of infection, but still requiring slow healing process and risking potential death. Limits of the other resources mean many have to settle for mundane healing still.
I want to know how this affects battle conventions in general, but for this question I'm focusing on how enemy wounded and medics are treated. In our world you DO NOT attack those who are too wounded to fight, and doctors/hospitals are very strictly off limits. Of course, in our world wounded are rarely going to end up fighting against you in the near future. It takes too long to heal. In fact leaving wounded cost your enemy far more in resources to tend to the wounded then if you killed the wounded.
In this world though leaving wounded may mean fighting them again next week. Most will still relay on mundane healing, all the rapid healing options are still limited in resources, but a non-trivial number can be rapidly brought back to the fight. Lets say after a week roughly 10% of wounded will be back up to mostly-fighting strength, with a mostly negligible number healed every day after since the easily treated are already healed. This assumes good supply lines, long campaigns would mean more careful triage of Alchemical potions and later battles may see less healing due to lack of supplies.
In this world will wounded or those that treat them be off limits? Or will they now be too large of a tactical threat to leave off limits? What are the chances that making killing blows on wounded is a standard tactic? Will flanking to get to your enemies medics and kill them be a valid and honorable tactic? Perhaps the rules will vary for healing: magical Healers are fair game, Alchemists are a grey area, and mundane treatment still of limits?
Related, what are the odds of something like the Geneva convention affecting this (there will be a neutral party that helps to negotiate these sort of conventions and has a limited ability to encourage sticking to a convention by lowering aid to sides that don't stick to them, but is not powerful enough to enforce anything if both sides don't want a convention)? Is it likely that sides will agree to either leave certain wounded/medics off limit or agree to emphasis saving most lives possible at expense of being able to heal fewer to the point where they may rejoin the fight; something that would be tactical suicide unless you're certain the other side will do the same?