Bayonets, trench knives, entrenching tool blades and sharp stones are inherently cruel, uncilivized and unquestionably legal in combat.
How far down the scale of disarmament we chose to let ourselves be taken obviously depends on how long we chose to let political entities emasculate us, how many unnecessary casualties we chose to take, and how long our enemies give us the option.
Having suffered firsthand the results of our politician commanders dithering around about words like 'proportionality' I say the Commander has a moral responsibility to use whatever weapons he has to accomplish the misson and save allied lives.
If you don't want to be a civilian casualty these days don't let the targets set up in your village. If they do, leave. The military aren't trick shooters and if you get your house blown away by the hit that takes out your neighboring terrorist way-station, well doom on you.