Shot, your right except most State forces comply with conventions and treaties.
In war people get killed. Death tends to be fatal and can be very painful too. Scientists, engineers and soldiers have developed ingenious and more lethal methods of delivering death.
Over time humanity has written rules to make death surer and swifter and horribly disabling systems banned.
Obvious weapons are gas and biological. More recent is land mines. Killing disabled combatants is another. Less memorable is banning dumdum rounds, introducing the full metal jacket reduced bullet fragmentation, introducing small calibre high velocity rounds overcomes that ban.
The problem today is the clash between State and non-State forces.