Untamed, The by Max Brand (1892 - 1944)

Whistlin' Dan Barry is one of the most interesting characters in Western fiction. With uncanny abilities he controls a wild stallion, appropriately named Satan, and a ferocious wolf dog, Black Bart. Easy going, Barry proves absolutely unforgiving when physically assaulted by a feared, vicious outlaw, Jim Silent. Seemingly without any emotions, Whistlin' Dan is relentless in his vengeful search for Silent and his outlaw gang. The is the first book in the "Whistlin Dan" series. (Introduction by rkilmer)

The Dan Barry series:
The Untamed
The Night Horseman
The Seventh Man
Dan Barry's Daughter