Ernest Hemingway's short story "The Undefeated" was first published in 1927 in his second collection Men Without Women. Also in this collection are the more popular stories "The Killers" and "Hills Like White Elephants." After his service in Italy in WWI (1918-1919), Hemingway traveled to Paris with his wife, Hadley Richardson, working as a correspondent for the Toronto Star. There he met writers and artists such as Gertrude Stein, Ezra Pound, Sherwood Anderson, James Joyce, and Pablo Picasso. Hemingway later became associated with Stein's "Lost Generation", a group of American expatriate writers (including Pound and Fitzgerald). In general, the term eventually referred to a disillusioned intellectual circle, or a group of elite artists killed in a war. It was most likely during this time (1921-1927) that Hemingway became interested in bullfighting. Years before he wrote "The Undefeated," he wrote a piece on bullfighting for the Toronto Star. During this time, Hemingway had a son, John (1923), divorced Hadley (January 1927), and married Pauline Pfieffer (May 1927). It is generally agreed that Hemingway suffered from some form of depression and a fear of abandonment stemming from being rejected by Agnes Von Kurowsky, a Red Cross nurse with whom he fell in love while in Italy and which likely inspired A Farewell to Arms (1929).

Much of Hemingway's writing is characterized by themes of pride, the struggle to maintain masculinity and durability in the face of natural, cultural, or artistic obstacles. In "The Undefeated," the protagonist is Manuel Garcia, a veteran bullfighter, who basically has to beg Retana, a promoter, for work. Retana finally agrees, giving Manuel a fraction (300 pesetas) of what the younger, more popular bullfighters are making. Manuel then goes to a cafe to wait for his friend, Zurito, a picador (a horseman who uses a lance to help the bullfighter). Zurito tells them they're both too old. He pleads with Zurito to "pic" for him, and Zurito only concedes after Manuel agrees that if he does not perform well, he will quit for good. Fighting with Hernandez, another up-and-coming bullfighter, they engage in a long battle with a bull. Readers get perspectives mostly from Manuel, but also from the audience, a bull-fight critic, Zurito, and even the bull itself. It takes Manuel five tries to stab the bull. The first four times, his sword either bends or bounces off as if, Hernandez says, "He's all bone." In the end, Manuel kills the bull, but is gored and rushed to to the doctor. While Manuel lies on the operating table, Zurito raises a pair of scissors to cut off Manuel's coleta (pigtail), a veritable castration which would symbolically end Manuel's bullfighting career. Zurito claims he was just joking, and the story ends with Retana quickly losing interest and Zurito staying to watch over Manuel.

This story is somewhat of a precursor to The Old Man and the Sea in that the protagonist is fighting nature (bull or marlin) and doing so in spite of his age and in spite of many people around him saying he has lost his ability. This fight, perhaps analogous to Herman Melville's "white whale," is often illustrated as a metaphor of Hemingway's own artistic creation. Note the symbolic connection between the sword, the fishing rod, the phallic symbol (more ostensible in works like The Sun Also Rises), and, of course, the pen. In 1938, in a preface to a collection of his short stories, Hemingway wrote:

In going where you have to go, and doing what you have to do, and seeing what you have to see, you dull and blunt the instrument you write with. But I would rather have it bent and dull and know I had to put it on the grindstone again and hammer it into shape and put a whetstone to it, and know that I had something to write about, than to have it bright and shining and nothing to say, or smooth and well-oiled in the closet, but unused.