Start a game on Impossible.
When 3 or more enemy units show up on the field, use your special ability. Make sure it kills at least 3 enemies.
Build the $200 turret so you can take advantage of how quickly it attacks and how much damage it does to more advanced units.
From now on, train Clubmen over and over again until almost the end of the game. You MUST do it as soon as you can afford it.
Use your ability as often as you can to help clear.
When new turret slots open up, buy them as soon as you can if you have the money, and then fill them with $200 turrets again.
Don't change into the next age. This may sound crazy, but the way the game is coded, your army of Clubmen and your turrets can easily kill an enemy unit in later ages. Plus, when enemy units reach the end of your territory, you can do a lot of damage with your Clubmen's army (causing all your clubmen to attack resulting in huge damage). With this setup, it should only take a minute or two to kill a tier 3 unit in the last age. The price of Clubmen is only $15, so every kill you make makes you money.
Keep doing these steps until you've made $200k and 400k experience. To get to the newest age right away, trade in two old turrets for two $100k turrets. You've pretty much won the game, so you can finally let go of your hand.
From now on, this is just like any other Age of War game: you keep farming to buy $100k turrets to replace the rest of your turrets. All of your units will die before they can even damage your base. Farm for $600k-$750k.
The rest of your money should go into Super Soldiers. Watch as your army destroys everything in its way, including its troops, vehicles, and base.
Congratulations, you have completed age of war on Impossible!