Thanks for the info. Another question though: Does a unit's HP affect the unit in the same way that defense does? Say a marine unit has 2 defense and 2 HP, would it take a unit with only 2 attacking power to destroy it?
HP is the amount of damage a unit can receive. For example: A tank does 6 damage to an infantry unit, this infantry unit would now have 1 HP (7HP - 6 damage = 1). Once a units HP is reduced to zero, it is destroyed.
Defense is the max amount of damage a unit will deal when it is defending. So an infantry unit will deal a maximum of 7 damage while defending (assuming it is in a city and you are using a strategy that does not affect infantry defense)
So, the answer to your first question is NO. The answer to your second question is YES, any unit with attack of 2 or above is able to destroy a unit of 2 HP regardless of defense. However, the attack stat is the maximum amount of damage a unit will deal; therefore there is still a chance that the attacking unit will not destroy the defending unit.