So, a long, long time ago in a place called Verden, there were lots of people who lived there. Some of these people were called Saxons and they had a different religion than the others. The people who were in charge of Verden, called the Franks, didn't like the Saxons' religion and thought they should change their ways and follow the same religion as them.
The Franks talked to the Saxons and told them they had to change their religion or else bad things would happen. But the Saxons didn't want to change their beliefs and they didn't want the Franks telling them what to do.
So, one day the Franks got really mad at the Saxons for not doing what they were told. They decided they were going to teach them a lesson and show them who was boss. They rounded up all the Saxons and made them kneel down in front of them.
Then, the Franks did a really terrible thing. They started killing all the Saxons one by one with their swords. It was really scary and sad. Some of the Saxons tried to fight back but it didn't help. They were outnumbered and outmatched.
In the end, a lot of the Saxons were killed and the Franks thought they had won. But lots of people were really upset and angry about what had happened. It was a really bad day for Verden and one that nobody ever forgot.