I adjusted the Attacker class army some to hopefully encourage the AI to use them. They take slightly more shields for a significant boost, but perhaps in the AI code it's not sufficient to switch to them. I tested Imperial class armies (which are regiments) versus Defender class armies (which are battalions) on rich farmland (which has an excellent defenses even without a fortress. That resulted in a win but with as little as 8 hp of damage (ie you crushed them) to as much as 96 (you won but it was a nail biter)! Whatever the unit value which is 12 HP is multiplied times ten ie a range from 0-120. An Imperial regiment attacking a Defender class battalion within a fortress resulted in the reigiment sometimes able to kill two who were stacked in a fortress( which is excellent to see the AI doing) but also 50% of the time resulted in the regiment dying ie they used up every last bit to take them out. Defensive battles with battles and regiments are not predetermined outcomes. They are delightfully risky with some spectacular outcomes. Rich farmland is a misnomer. It's the pinacle of terrain modification that incorporates military engineering with agricultural upgrades. I need a better name. I had considered an intermediate so it takes a longer time to fully upgrade but some of Japan has swamps that were historically drained for habitable use. So I may still use that swamp terrain.