He broke the mold. The traditional responsibilities were not enough anymore. You had to be adroit at international politics. You had to be a skilled diplomat. You had to be savvy with the press, and you had to be a really sophisticated leader of a large organization. When you judge McKiernan by Petraeus's standards, he looked old-school by comparison."
So basically the mould breaking was being like the majority of successful wartime leaders anywhere on the planet in the last 3,000 years.