Fox

"The use of horses, mules, and other draft animals increased exponentially as the various conflicts dragged on. This was especially true for groups such as the Appalachiastani, Al-Rockie, and even the Confederacy of Independent States (CSI) after major oil refineries had been destroyed or had ended up with the opposing side. What little fuel they had was usually acquired from enemies that still utilized vehicles as their primary mode of transportation."

"Horses and pack mules though were better suited than most vehicles for many of the mountains and other rough terrain these conflicts were occurring in. Able to haul tons of materials without straining the fuel supply, they became a highly sought-after and protected resource. Some groups even formed dedicated calvary or dragoon regiments, something that most modern military historians had declared dead with the advent of the machine gun and tank..."

Excerpt from "The Modern War Horse" by W. T. Fox