Ineed writing a story, can someone me with what i should wright the story about and how i should wright it?

here's the topic i have to wright about:

an example of some bad behavior that needed correction, and something that happened which naturally corrected it.

So you are the king of more than half the earth and you have the strongest army when you  hear about some other kingdom different you go to conquer it on the way you hear ants saying here comes the king were dead so the king heard this and turned back because his army would easily destroy the other