A tip...stay in ia a longgggg time.....untill ia the game was great for me, then came global....me being used to have a difficult time in new ages until you upgraded the armies, well...global is different...upgrading armies takes longggggggg and dont add to much, spend all my global time (months, Almost half a year!) Chasing ia bases, cause global bases have way to heavy defenses (or i had way to weak global armies, anyway you wanna see it)...now atomic, got half my armies upgraded (core ones, tanks, artillery, shooters)...still got my ass kicked when attacking global bases with half upgraded defenses....army strength of global and atomic should be much greater, especially for the amount of time/resources you have to spend to get it done (2 stables upgrades at 10 or 12 days a piece? What??)...in global/atomic, make sure you have really, really fierce looking walls, cause thats the thing ppl think twice about, not the strength of the armies.
Would be so nice if every army upgrade just would ad 1/3 of the strength of the army an age lower instead of waiting 10 days for so ething like 7 attack points....lol