I suspect that Hawk was referring to the fact that Mulcahy was young, for many priests. Many of the priests in the war were much older. If you think about it, it it can take years to become a priest, and since many do so a bit later in life, they're gonna start older. I highly doubt they'd put a brand new priest in a war zone. Even those that start right out of college. Add a minimum of 5 years to that, making the first priests in their mid 20s, at the earliest. Add in a few years of experience, you're talking early 30s. Therefore, relative to other priests in a war zone, He was relatively young.