The SNES Civilization game can be tricky, you have to be equal things diplomat, economist, and military strategist. But, sometimes things just don't go your way.
Like occasionally your tank will be killed by a warrior with a stick for a weapon. Or your cannon gets destroyed by a diplomat with zero attack strength.
It happens... somehow.
But, you can minimize damages.
The game is designed to let you save anywhere, so long as it's your turn. So all you have to do is save right before you attack someone
And then if you lose, just quit and reload the game. Keep on reloading until the battle goes the way you want.
Tedious? Yes. Cheap? Yes.
But, hey, it's a single-player game, so it's alright.