As Belarus I watched as my ally Romania invaded Ukraine. They made a good initial raid but their older equipment was being worn down and soon they were on defensive. I joined in to help and declared war.
Ukraine AI withdrew most of its units from Romania to face me but here the first problem started: I had set up a line of emplacements, entrenched with masses of artillery behind and AA sites. Ukraine just sent waves of units at my defenses and they were shredded. Sure, few were totally destroyed(mostly infantry), but they withdrew in such bad shape that by casualties they were losing worse than 10:1. The thing that I will come to later is that the AI doesn't seem to count that well or examine what it faces. After this Somme like offensive, Ukraine calmed down a bit, but kept sending a trickle of units as available to get blasted.
Later on after attacking and taking Kiev, I left Ukraine base in west to watch Romania and Ukraine bleed each other. Ukraine built lots of artillery and the base protected a town. Romania would send 2 or 3 units to take town then sit there getting blasted by artillery till they withdrew. Then Ukraine would send a unit to re-take town, then Romania would send 3 units to re-take it etc. Now, around the capital Romania was making a 'blob' of masses of units, tanks, artillery, infantry. Instead of launching one decent attack, they just got worn down losing 100,000 men and 100 or more units doing this back and forth!
Like the first example, the AI just doesn't seem to even count force disparity or content. Surely there should be a routine where the AI goes 'Aha, I met 10 units, half artillery and got beaten so I need 15-20 units with high protection from artillery to counter' etc.It not real AI of course just a formula, so shouldn't be impossible.
Secondly, I'm sure you guys all know the 'Blob' tactic by now. The AI leaves his borders open more or less and sits around the capital and bases with ever larger blobs. Now the blobs can be tough, but if you just charge in with lots of heavy armour, then after the first line of tougher units, you tend to just rout the artillery and supply trucks by the hundred. Apart from silly build orders, the big problem is that defense isn't done realistically.
Maybe when designing a scenario, there should be invisible 'lines' set by the designer for the AI along with their direction, so that during the game the AI will be encouraged to build fortifications or deploy units in an intelligent manner, entrenching infantry and AT with artillery and AA behind and having armour around for counterattack and a mobile reserve. Sure, this is scripting, but isn't that what AI is in computer games in reality?And it would kill off the blob! You could also have a more dynamic AI for offensive, but if on his own land, then it would switch to a pre-planned defense as much as it could.