Carn was the relatively new commander of Rabbit Army when Dragon Army received their orders for their very first battle against his army. Carby was late to make commander at the age of 12 and was therefore not as cocky as some who made it at eleven. Ender Wiggin knew that Carby was a good soldier, but also knew that he would be using formations in his battle plans. After being thawed from losing the battle, Carby came over to Ender and congratulated him, making a lasting impression on Ender.
When Carby graduated, Bean was assigned as the new commander of Rabbit Army. Carby was sent to Tactical School, and met up with the rest of Ender’s Jeesh as they traveled to Command School.
Carn was one of the few characters introduced in the Ender's Game short story that carried over into the novelized version.
"They won't believe me when I tell them you did things that nobody's ever seen before. So I hope you beat the snot out of the next army you fight. As a favor to me."