When Burroughs writes his Indian tales, all doesn’t come 100% from his imagination and researches. He indeed was in the American cavalry… for ten months!

 Burroughs always dreamt of a military career, which was synonymous for him with adventure and romanticism. Shortly after graduating from the Michigan Military Academy, he fails the entrance exam at West Point. Whatever, it wouldn’t prevent him from living his dream, and if possible, in the “worst” post of the United Taste. What did he ask for! In his mind, “the worst” was probably “the most dangerous, the most exciting”. In the recruiter’s mind, the “worst” was just… “the worst”…

 On May the 13th of 1896, soldier Burroughs joins the 7th cavalry regiment at Fort Grant, Arizona. The colonel is a fat impotent, the sergeant a beer belly, and both are universally despised by their own men, whose duty mostly implies road maintenance! He catches rapidly a severe case of dysentery, since the only water available isn’t drinkable anymore due to heavy rains at the time. At the hospital, doctors diagnose the young man a heart condition, giving him six months to live at most, but really, he could fell down at any time…

 During this time period the renegade known as Apache Kid and his band roam the countryside, and the 7th of cavalry is called as backup. At last, some action! Burroughs crawls from his hospital bed to take part to the chase… All he would get from this is the more than reserved welcome of the Mormons of Salmonville, who prevent them from having access to their water! He would also discover the joys of sleeping outside, rolled in blankets so thin soldiers called them “Chicago Heralds” (from the name of a newspaper), drenched in humidity and horse sweat.

 Among the good experiences, his encounter with the 24th of infantry composed of black soldiers he will find very impressive, without exception, and his few contacts with Indian scouts. One of them has “bought” his commission by bringing to the soldiers the head of one of Apache Kid’s close ones!

 But all this is to no avail, the life at the fort is not what young Burroughs expected, and he soon pleads that his father uses his influence to get him out of there! It’s not very difficult, since the doctors had declared his heart condition was critical. Edgar Rice Burroughs is relieved from duty on March the 23rd of 1897.

 All the details here : http://www.erbzine.com/mag34/3469.html