Getting Throug Hard Defenses:
If there are a lot of enemy tanks gaurding their base, build about five cheap tanks and a lot of heavy tanks. (Apocalypse, prism, etc.) Order the cheap tanks to drive directly in the base and then quickly use what's left of them to get the heck out of there! All the enemy's should follow them and then you just ride in with the heavy tanks and wipe them out, all of them!