Hi Desert,

The rationale for the destruction of Jericho was clearly announced in
the narrative. And indeed elsewhere, the rationale is as far as I can
remember always announced

I  don’t really see the relevance of that. The ‘rationale’ for the genocide is part of the narrative, so open to the same critiques. 

Perhaps you would say the same about vengeance? Is it not a core
principle of OT ethics that vengeance is the Lord’s? God does it but we
are not allowed to.

I’m not sure what you mean by me saying the ‘same thing’. However, I would argue that the reason we are told to leave vengeance to God is because we do it vindictively, whereas he does it mercifully. God’s "vengeance" is of a different calibre to ours. It’s not that he has the right to be more violent than us, but that - specifically because he isn’t - he is safe to take care of what we would call "vengeance". We don’t do it
very well. We lash out in anger and hurt, whereas God deals with his
"enemies" by loving them and taking the rap for them.

Is it not a core principle of OT ethics that vengeance is the Lord’s?

Maybe we’re talking at cross-purposes here, but I’d say that the core principle of OT ethics is love.

The initial destructions under Jericho were commanded by God specifically, as were some others under Saul and David.

Well, that’s what the texts would suggest, but I don’t see any compelling reason to leave them unquestioned.

I don’t believe the teachings of Jesus contradict this principle at all
as they are principles on how his followers are to act… He didn’t change the teaching of the Old Testament.

As for the latter statement, of course he did! As for the former, if Jesus didn’t contradict these "principles" that you see, should we really be able to picture Jesus saying, "Love your enemies and do good to those that persecute you, unless God tells you to go to battle and wipe them off the face of the earth. In that case, feel free to kill as many men, women and children as you like. In fact, take some of the men into slavery and the women as your wives, if you - or your leaders - hear a Voice telling them to do so."

If Jesus doesn’t take precedence over OT "principles" then he is irrelevant for me and my world.