The only ones who were members of the Slayer Corps who were not allowed to take part in the Operation Liberation were the D Rank Slayers, to be clear, they were mostly made up of children who were still not even remotely good at using their affinities. They would not even make for good meat shields or baits in a real battle at all.
A couple of Enforcers stayed back in the Grand Castle as well as the High Council's members. The old cretins did not even volunteer to take part in the operation. But, it is doubtful that they would even perform well because of their age. "Come here, children, hide in here." Willis, the leader of the High Council was the one who was tasked with directing the D Rank children where to hide in order to be safe.
