Every incremental game needs a great simple core idea. You got that covered definitely. Now you need to add two things: a progression pace that feels rewarding and interesting and more "addons" to spice things up long term. I see A LOT of potential there. So much that I will wishlist you and buy you BUT only if I see the addons:

fight armies on two fronts surround enemies ice maps rivers bridges heroes mega units flying units line-attacks dodging units buildings towers

there can be so much good stuff there that add little twists. I hope to see them in the final release :)