Although he had access to several preprints that were shared among the practitioners of the field, he reproduced many proofs that had already been discovered by other researchers and published them in his early papers. Aschbacher only became interested in finite simple groups as a postdoctorate. He wrote his dissertation in combinatorics and was able to utilize many techniques developed in this area to make early contributions to the study of finite simple groups, which surprised the community of researchers. In particular, Daniel Gorenstein, another leader of the classification of finite simple groups, said that Aschbacher's entrance was "dramatic."