Why do you think the author has chosen to place Ender in an army that does not allow him to take part in battles?

They want someone that can lead and articulate battles more than fight them. Two adult voices, Graff and General Levy, discuss Ender once again. The General is not sure that they want a boy who would dig through the Giant's eye, but Graff points out that "what matters is that he won the game that couldn't be won." They decide to promote him from the launch group ahead of his time.