I happened on this strategy by accident but im sure it will work every time.
If your like me then the turn war breaks out you move all your def. units to your borders and form an unbroken line.
sometimes they are already in place to keep out settlers.
Well when you form your line leave a tile or two undefended.
make sure that its Grasslands or plains/desert behind the gap.
Now the AI on their turn will rush every available unit in range(this works best when rails have been completed up to the gap)
thru the gap.
On your turn surround this "army" with strong def. units and bring up all available artillary and Bombers if available(if you can pin them by the sea even better as your ships can then join in the fun).now you just simply bombard the crap out of them.
then use any fast units to hit their stack.Even if you lose a few of these attacks(I did) your fast unit will dissengage not die.
Now whatever is left of the enemy on their turn will attack to try to break out and they will die against your entrenched def. units.
on your next turn you mop up.
When this happened to me the enemy rushed 31 units into the gap.About half were infantry and the rest were swords and spears.The Infantry took the bombardment first and also def. against my armor and cav. so when it was their turn all they had left were like 10 obselete units.some tried to break out and died trying the rest just sat there for me to destroy on my next turn.
SCORE?--AI minus 31 units ---ME --NO losses
Try it -it works.
