Okay, but not very fun
My main gripe with this game was that it was not very fun or rewarding. You just went from level to level clicking buttons and watching a rather dull battle unfold. The difficulty was weird; it went rather quickly from easy to moderate to very hard, and the fact that cavalry and saboteurs were completely useless did not help. The graphics looked alright, the menus were quite nice, but the sound was annoying, repetitive and tinny. Overall, it felt like a pre-Command & Conquer strategy game from ten years ago.
How could it be improved? Options to adjust the way your army fight mid-battle, a more gentle learning curve (and perhaps selectable difficulty) , better balanced troops, and more enemy variety.
I would love to see an Invasion IV with all the above adopted.