Operation Berkshire was a secret plan made by some important people a long time ago. They wanted to study what would happen if there was a big explosion in a place called Portsmouth that made a lot of noise and vibrations. They thought it could help them make better bombs to use in wars.
So, they arranged for some big bombs to be dropped from planes and exploded in a place close to Portsmouth. But they didn't tell anyone living close enough to the explosion that it was going to happen. This was not a nice thing to do and could have hurt people and animals.
After the bombs exploded, the people who made Operation Berkshire studied how the explosion affected the ground and buildings nearby. They learned some things that helped them make better bombs for wars.
This operation is not something that should be repeated because it was not a nice thing to do and could have caused harm. We should always try to find peaceful ways to solve problems instead of using violence.