Go to the preferences screen and set your side to 250% on the percentage bars along the right side of the screen. This will make artillery, armor, and Infantry much more powerful. It will also make them harder to be destroyed. Set the enemy to 30% and you will be able to decimate the enemy.
Powerful tank
If you have the OOB editor, create a tank and put all armor plates to 255 and the angle to 125. This will make you new tank much harder to hit, and make it withstand a lot more hits than normal armor.