We were stood outside Caenarfon Castle in Wales.
Many years ago, people used to live in this castle. From time to time, their enemies would try to attack it.
I thought of how to attack a fortress like this. What were its weak points? There didn’t seem to be any. As defences go, it was formidable.
So I asked my friend Eric. He knows stuff like this. “What would the weak point of a castle like this be?” I asked. “The doors maybe?”
He shook his head. “Simpler than that” he said. “The weak point was to put it under siege. To stop food and supplies getting in.”
That’s the thing about defences. The stronger they are, the easier it is for them to become a prison.