Slitherine

I'm trying to set up movements for two AI groups with "move to hex", checking the "ignore enemy" box. I also tried "defend hex" with a range of zero.

Still, the AI units engage defenders in sight, never reaching their destination, or move way off the target by themselves.

I also have a problem with artrillery units tasked with "defend hex" pointed at an enemy hex with a bunker, and refusing to attack said bunker. If they have other targets in range, they bombard it, otherwise they do nothing.

Try 'move to' and set aggression level at 75 or higher. I've never had a succes checking the 'ignore enemy'.
The AI tends to attack the weakest enemy in range. You could try 'search & destroy' for artillery (maybe remove any transport) and restrict the target type to 'structure'.

I have found, and I believe it's been confirmed by officials, that these commands tend to be advisory in nature. That is, if the AI sees an opportunity to knock off a weak unit, or it wants to go after or defend a supply hex or VP, it will override commands to the contrary. Conversely, if it deems an attack to be unwise or a waste of resources, it will refuse. As Erik says, for those commands that have aggression settings, "50" seems to say "If it's okay with you, AI, would you mind doing this?" "75" seems to say "Look, I would really like you to do this if at all possible." "99" seems to say "Do it or else!" without defining what "else" means, since you cannot fire the AI in this game.

No value or order I input seems to avoid three motorized infantry units to swerve off-course by 5 hexes to crash into a fortified infantry line.

Artillery still ignore any bunker, and there is no "search and destroy" for land units, unless I can use naval/air s&d commands on land units too...

Great, now that I figured out how to make units go to hex just by making them move waaay off any hostile unit they could be diverted onto, they refuse to switch to a different order via trigger.

I give up.

I don't remember how I did it, but I made it work and never had the same problem again...

Stucco,
I have found that it is extremely difficult to make the AI cooperate on even a simple combined arms attack. I was helping Erik on the battle of the bulge trying to design a sustained AI attack, and had to give up.
In my Salerno campaign, I had to put like 3 or 4 times the actual number of German battalions to mount a determined, effective attack on the Allied landing forces.
In my humble opinion, the AI is designed for defensive operations at given points, or broad, general attacks. Not sustained, determined combined arms attacks on specific areas or along designated axes of advance.



conboy