Our division lost four experienced leaders, three junior lieutenants, and a major, all during the first week of our first campaign.

This sentence is a bit confusing to me. I do understand that the 3 lieutenants and the 1 major are describing the 4 experienced leaders, but I still think the punctuation here is a bit of a problem. At first glance, it could appear that the officers named are in addition to the experienced leaders, laid out in a list form, but the final comma refutes this. I propose that the sentence actually contains one comma too many. While the first and last are needed to set off the parenthetical phrase, the middle one is not needed and gives the appearance of listing. More correctly, it would appear thus:

"Our division lost four experienced leaders, three junior lieutenants and a major, all during the first week of our first campaign."

Source: World War Z, p. 295