I'm not big on idlers but this was just excellent. It's really fun! Please develop it even further.
Some remarks:
There's no need for enemy base to have that many hitpoints. When you kill all of their troops. you've practically won the round but still need to wait quite a bit until your units deplete all of base's hitpoints even though there's no any resistance.
You know what could be cool; instead of killing the base, let your units take it. Scroll the screen to the right and now the occupied base becomes you new spawning base while your existing units keep on pushing forward. That way you get a more satisfying sense of progress/persistency and the scenery can gradually change as well. The game can show how many bases you've advanced and there could even be some boss base at the end of a section. The enemies could also take the base back and you're then forced to retreat to the previous one.