From: Houston, TX
Of course it was cooperative. And there was no disengagement attack whatsoever. You miss the point.
I wrote "So i repeated this procedure with toaw_log on and removed all artillery support from the ground attack". I did a deliberate test with just those two attacks, no other artillery, air whatsoever involved. Artillery that has been ordered to a mere bombardment against hex A participates directly in a battle in hex B with cooperative units (not "xy supports".., no the combat report states "xy attacks.."). According to toaw_log it really participated in that attack (i know this because there was no artillery support to that attack and toaw_log states "132 kg/min weight of long range fire...") and it lost 20% supply instead of 10%. And it was one combat round.
Yes, that occurred to me after I posted. However, I've tried to recreate this with a test scenario and I haven't been able to do so. Bombarding artillery doesn't support (or directly attack) nearby, in-range, assaults. And they lose 10% supply, not 20%. So, at least, the above isn't the general case. Something weird has to trigger it. But what?