The United States Camel Corps was a mid-19th-century experiment by the United States Army in using camels as pack animals in the Southwestern United States. Although the camels proved to be hardy and well suited to travel through the region, the Army declined to adopt them for military use. The Civil War interfered with the experiment, which was eventually abandoned; the animals were sold at auction.
Beale wrote very favorably about the camels’ endurance and packing abilities. Among his comments was that he would rather have one camel than four mules.
And because you brought up horses I’ll bring up mules which some nations’ militaries use in mountainous regions.
Not current, but:
https://en.wikipedia.org/wiki/United_States_Camel_Corps