Slitherine

I'm kinda new to scenario design in this game, so please bear with me as a newb.

Is there a way to set the AI to carry out a series of phased withdrawals or delaying actions? IE for the human player to be on the attack and have the AI slowly give ground, preserving their units? Or is that a behavior I can only get from another human player?
I'm specifically working on some Philippines scenarios and it would be nice if I could have the US/Philippines side withdraw and not fight to the death for every objective.

Yes. There is a possibility. You need to work on the sequence when a certain hex is captured or retreat starts on a certain turn, or when the AI suffers a certain casualty. Then the specified unit must be reassigned to the AI team that is to behave in a given way.

Absolutely yes, with the proper triggers.

You can set certain AI groups to retreat to a certain location with Defend Hex as soon as a certain condition is met. Said condition could be "player conquer X hex", or "unit strength <x value". You can also set up a turn-based trigger, if you want the withdrawal to begin at a certain point even if the conditions aren't met.

You can also set up a retreat if supply connection is severed between two given hexes, meaning the AI will try to break out of an encirclement.

You can also set up the retreat conditioned by other triggers (say: unit spawns or such).

The system allows for a lot of complex maneuvers, but you'll need a lot of triggers and AI groups.