Keep the green men away form your fort. It starts to get better around level 5. I played untill level 32. I bought all the barricades, autodefence, and I ended up with 20 gaurds on duty that I didn't even have to shoot anymore. The airstrikes would be the best defense there. It's kind of fun. http://www.i-am-bored.com/bored_link.cfm?link_id=10781
i got so bored,ive been playin for 5 hours(doin other things as well) Im at(so far)the 76th level, have 2607 tower guards on duty,196 Com Hubs on duty,30 repair people,and all the barricades and AutoDefences
"Whatever doesn't kill you will.....well,it will hurt like hell, but it wont kill you."
The airstrikes would be the best defense there. It's kind of fun. 
