I don't know if this is the kind of strategy game your looking for but I find it lots of fun 
It's called war agent, but it does cost a small fee I belive
https://play.google.com/store/apps/details?id=com.bazinuinc.waragent
It's called war agent, but it does cost a small fee I belivehttps://play.google.com/store/apps/details?id=com.bazinuinc.waragent