People...once you can...Get upgrades for all of the generals, and upgrade the charger to an EMP w/ Level 2 and upgrade the charger to a blaster w/ Level 2. Also upgrade NORMAL drone tech.
Guys, if you capture a city and the surrounding cities are red, unless you feel confident, DO NOT GO TO THAT CITY.
Red cities attack you when you come because you "took other cities." If they are stronger than you, and you die, you will respawn at that red city and be forced to fight them again. This is the reason why I had to make a new file.
BEST TIP EVER:
Unlock the grenades and rockets as soon as possible. DO NOT upgrade shotgun/machine gun. The former are overall better at killing than the latter, in terms of cost of upgrades.