Discuss the interaction of War Weary on an Army with a Field Commander as its commander, if there is an interaction.

Following

RAW I think Field Commander doesn't interact with War Weary's effect. War Weary assumes you're using your commander's courage value (which vehicles obviously don't have), Field Commander has you treat your units as if their own courage value is 2 as long as they're within range 1-3 of the Field Commander unit. War Weary even specifies a unit of commander rank, and Field Commander doesn't change the unit's rank. RAI I think it's most likely an oversight on the devs' part, and I think the language of War Weary will probably change whenever they get around to it to include units affected by the Field Commander aura.

I agree with Han Singular, by RAW they clearly don't interact with each other, so even if you're playing War Weary, your units at range 1-3 of your field commander will be treated as having a courage value of 2.