Ok, I give you this problem to solve after this chapter. Would you rather:
A) Spend 70k of your men to kill 70k of your army to achieve victory, spending time and resource that could be use for future battle
B) Torture, massacre 1k of civilians to send a message to the enemy, making them surrender to you without loosing any men for both you and the enemy
Kanki chose option C) torture, massacre 1k of civilians to send a message to the enemy, then
also fight a battle anyway, losing men on both sides, while letting their top generals escape to plague you in future battles.
but besides, this isn't a trolley problem. The whole point of a military is to fight and die so that civilians don't have to. When you do stuff like this in order to win a battle we call them "war crimes".
You don't consider that the soldier you are killing are civilians that are force to fight you, that is just cruel of you. Besides Kanki did the right thing, he killed the Zhao main commander, force them to retreat most of their force so taking the hill was easier and less wasteful
They have weapons, they're in formation, they can defend themselves, and are actively engaged in military operations. Those are "soldiers". And however much they were "forced" to fight (let's not get into how conscription/volunteerism worked in ancient Chinese military) they're certainly more engaged in this battle than the innocent civilians that Kanki murdered.
Your inability to draw a distinction between civilian and military targets shows an alarming ignorance of how the world works, and your eagerness to go to bat for Kanki shows a depressing lack of empathy. I hope you don't take this sort of view in regards to real-world events.
You've also completely misunderstood Kanki as a character if you think he did it this way because it was "less wasteful", he did it this way
because it was cruel. And easier, yes - he takes the cheap way out whenever possible. He doesn't think about long-term consequences to his actions, such as paving the way for peaceful integration of the rival states, he just wants to inflict as much pain on the world as possible while hanging out with his best buds. I think he's a fascinating character who gets more development later, but you have to be out of your mind if you think the manga wants you to think "Kanki was right" about anything.
