I purchased this and a few other pieces by Pierre Albert Leroux (1890-1959) from a dealer in France I found online-- I just fell in love with the sense of intimacy they lend to their official, uniformed subjects (including this horse, which looks like quite an old soul to me) and no-fuss manner in which they were done.
While I might have guessed that he was self-taught, I have learned that Leroux, born in Versailles, trained under Academic history painters Fernand Cormon and Jean Paul Laurens and exhibited at the salon of French artists. He did his military service as a musician in an infantry formation, and later became a stretcher-bearer. It was during these years that he made his first sketches and watercolors of combatants, which he became known for.
Ink and watercolor on the back of what appears to a letter/advertisment from a Parisian seller of hygienic wash basins and medical equipment. There are fold lines running both horizontally and vertically across the center and various ink stains etc. 12 1/4" x 8". Signed and dated what looks like 1908.