The House of Clarence had given birth to generations of outstanding military men. The current Duke Clarence was one of the three generals of Griven, and his son, Arthur, was a lieutenant colonel.
Meanwhile, the main business of the House of Milton involved mining and weapon forging. That was the reason the two families, the Clarences and the Miltons, had a rather close relationship.
The Miltons were a powerful family with a strong hold at the royal court. If Arlan wanted the Miltons to receive proper punishment without causing friction among the aristocratic and royalist factions, Arlan had to prepare so there wouldn't be any escape for them. For that his friend Arthur Clarence would be of great use.
