After the incident in Reginald's land, Ren told Henrietta to announce to the other noble houses that Duke Reginald had already surrendered and was now serving under him. Although, he didn't really need to announce that since even without Reginald the other noble houses will most likely bow down to Ren.
When they learned that the armies they sent alongside their family heads and heirs had been massacred, even if Reginald was able to somehow escape, and continue his supposed crusade, the current noble houses would never think about opposing Ren again.
...
Those that were able to somehow survive that day had returned and reported to their superiors about what had happened.
Despite the contents of the report were unbelievable, they had no choice but to believe it. Since the bodies of those that died that day were still in the city. Of course, in the beginning, they had their doubts.
