In case anyone else had the same question I had.
“All's fair in love and war.” A very famous phrase. But, if “all is fair”, how can it then be the case that people can be said to commit war crimes?
When I was little and asked my father what a war criminal is, his response was “the loser”. In the years since, I managed to figure out that this is not quite the case. There exist laws that govern war, that create a clear separation between “war crime” and “business as usual”. There are even cases where something that's legal for civilians is nonetheless a war crime for combatants!
Some war crimes are easy to imagine. Chemical or biological weapons, for instance; anything whose use would lead to wide and indiscriminate deaths for both sides of a conflict. Interestingly, “chemical weapons” include pepper-spray, which is an example (quite possibly the only one) of something which is legal for civilians but not for combatants. (Mainly because, in civilian life, one can be fairly sure it's not something worse than pepper-spray. Combatants don't have this luxury.)
But those war laws are easy to imagine. The more interesting war laws govern mainly the following thing:
There must always be a clear line of demarcation between combatants and non-combatants. Non-combatants must always be safe from combatants, but the same must hold true the other way around.
Examples of war crimes:
- Attacking a medic
- Attacking while being a medic.
- Executing someone who has surrendered
- Fighting after having surrendered
- Attacking civilians
- Attacking while disguised as a civilian
- Attacking someone who has raised a white flag
- Attacking whilst having raised a white flag
Similarly: Disguising oneself as the enemy to infiltrate enemy lines is perfectly acceptable, but attacking others while so disguised is a war crime.
So a good tl;dr for this article would be “Attacking the helpless is a war crime, but so is feigning helplessness in order to attack”.