He also distinguished himself as a member of the U.S. Marine Corps Reserve — receiving the Navy Cross for his actions during the Battle of Guadalcanal and retiring as a brigadier general.

Having joined the Virginia National Guard in 1931 and served on its rifle team, McIlhenny transferred to the U.S. Marine Corps Reserve in 1935, attended Platoon Leaders Class, and served as captain of the U.S. Marine Corps Reserve rifle team.

McIlhenny would draw on his experience with the mid-century "C-Ration" to produce the Charlie Ration Cookbook or No Food Is Too Good for the Man Up Front.

A bon vivant and gourmet, McIlhenny was closely acquainted with many luminaries of the food world, such as James Beard and Paul Prudhomme.

McIlhenny was an avid hunter, participated in many big game hunts in the U.S. and Canada, and went on several African safaris and Indian shikars.