Concerning myself, I am moving along very slowly... Some day I shall begin to do things, until then I merely scratch a living. Between you and me, I wish I had never opened the books. That's where I was the fool.
London was 26 years old, a college drop-out, and his marriage to Bessie Maddern (who, he said, he married out of friendship rather than love) was not happy. The woman he really loved, Anna Strunsky, had moved to New York. Even so, while in the Klondike he had read John Milton's Paradise Lost and Dante's Divine Comedy and he determined that he too could be a great writer.
About a month before the letter quoted above, London published his first short story about a dog, originally titled "Diable — The Dog." In it, a half-wolf, half-dog named Diable (later re-written as Bâtard) is brutally tortured by his owner Black Leclère. The dog becomes angry and violent, earning the nickname "Hell's Spawn." One night, Diable takes revenge by attacking his owner in the night. Leclère survives, but refuses to have the dog put down, reveling in their violent bond. When Leclère is falsely accused of killing a fellow prospector, he is tied up, and Diable finally finishes what he started:
...His eyes chanced to fall upon Diable, head between fore paws and stretched on the ground asleep... He studied the animal closely, striving to sense if the sleep were real or feigned. The dog's sides were heaving regularly, but Leclère felt that the breath came and went a shade too quickly; also he felt there was a vigilance or an alertness to every hair which belied unshackling sleep. He would have given his Sunrise claim to be assured that the dog was not awake, and once, when one of his joints cracked, he looked quickly and guiltily at Diable to see if he roused... A few minutes later [the dog] got up slowly and lazily, stretched, and looked carefully about him... Assured that no one was in sight or hearing, Diable sat down, curled his upper lip almost into a smile, looked up at Leclère, and licked his chops.
*Some of the information from this post was found in Jack London: A Life (1997) by Alex Kershaw.