If you throw away your principles because you are fighting an unprincipled enemy, you are no better than them.

That's a lovely thing to say, but if your existence is being threatened by an aggressor, I wouldn't blame you for throwing out the rulebook.

In my view, if someone invades your territory and starts attacking you, you have no obligation to follow any sort of "principles" or "rules" when it comes to how you fight back. Anything you need to do to the attackers in order to defend yourself and your people is, by definition, morally defensible.

(Do note that I said "need". Doing arbitrary messed-up things that don't actually further the goal of driving back the attackers is not ok.)

FWIW, during the Iran-Iraq war (where Iraq invaded Iran), Iran used a bunch of pretty questionable tactics like suicide squads of child soldiers.

It’s such a shock to the system to realise that “unprincipled enemy” referenced here is the US.

And it seems interesting a lot of people seem to be completely oblivious to it.

There is no if. We've already done that. So yes, we are no better than them. So answer the question. Why would Iran follow conventions it's enemy that started a war of aggression is not following?

Becaus two wrongs don't make right. If they are smart they will stick to the convention.

They tried restraint and proportionality for decades and where did that get them? 47 years of non-stop aggression, espionage, sanctions and the mass deaths of Iranian civilians.

America has never played by the rules.

US exceptionalism is a prominent feature of every republican and democratic president since decades.

It's sad, because if US did, and led by example, it could've pulled serious weight internationally on plenty of matters.

Instead it can only do so by economic or military leverage, which, at the end of the day is not enough of a leverage to avoid confrontation.