Everyone has commented on how stupid the guards are. What about the bosses? They will walk right up to you, you can just stand there and they will impale themselves.
Here is an excellent stragety: pick the undead. Buy the halberders, then just send them all down a single row. Even if the opponent flanks you, let them go, unless the problem gets serious. All the halberders accumulate together, and kill fast. When they penetrate enemy lines, they don't stop comming. This stragety worked so well that for my first battle in the campaign, I beat a Demon territory easily.
Just for everyone who is complaining about the water spells, you just use the army dudes deep blue gun. Not only is it an excellent weapon for fire, but upgrading it makes it summon a fume of water under the enemy! (Note: got this somewhere in a chest at the ocean level, can't remember which :(
 "Lucky Tower"){kind=icon}
 "Protec the Castle 2"){kind=icon}
 "Balloon in a Wasteland"){kind=icon}
 "Ultimate Assassin 2"){kind=icon}
 "Sushi Cat"){kind=icon}
 "Bunny Flags"){kind=icon}
 "Epic Combo!"){kind=icon}
 "Wake Up the Box 2"){kind=icon}
 "Warlords: Call to Arms"){kind=icon}
 "GunBot"){kind=icon}
 "Epic Battle Fantasy 3"){kind=icon}