There are a number of variations of a story on the internet mentioning how a ruler/an army accepted Christian baptism except they held their sword arm and sword out of the water, rejecting any limitation on their ability to fight.
This source says this occurred with Charlemagne:
Actually, Charlemagne was the most powerful European ruler of the Middle Ages, leading a people called the Franks to rule most of Europe. Under his rule, many people got baptized into the Church. It was pretty much expected of his soldiers, for example. In fact, they would go down to the river en masse and take the plunge. But one source reports that there was one thing that was a bit unusual about the baptisms of those soldiers. When they would go under the water, they would hold one hand out of the water with their sword in that hand. They didn't want that hand baptized. That was the one they wanted to be free to use to kill whoever they needed to kill.
On the other hand this source links it to Ivan the Terrible
As the words were spoken and the priests began to baptize them, each soldier reached to his side and withdrew his sword. Lifting it high overhead, every soldier was totally immersed-everything baptized except his fighting arm and sword.
I originally heard it in a talk given at a camp, where the story was attributed to have occurred with Roman soldiers. Was this a common occurrence? Or did it happen at all?