ON A WET Sunday afternoon in October 1935, a 29-year-old director of a New York publishing house began a new children's story. Munro Leaf had already written two books for boys and girls with his own pictures, but for some time he had wanted to come up with one for his friend Robert Lawson. The artist needed the work. He had had only slight success so far as an illustrator for juveniles and was struggling to live off his fine etchings. The new story had to be tailor-made to Lawson's special talents. He could draw animals beautifully, but cats, dogs, horses were everywhere in the picture books of the day. Leaf wanted something novel. He finally settled on the story of a bull. Although he had never been there and had never seen a bullfight himself, Leaf set his fable in far-off Spain. He called his hero Ferdinand, from Ferdinand and Isabella, the only Spanish names the writer knew. And the story had to be funny, so Leaf made his bull a gentle beast who prefers to sit in the shade of a cork tree and smell the flowers.

As with so many classics of children's literature, The Story of Ferdinand seemed to write itself. Within 40 minutes, Leaf had the manuscript ready to show his friend. Lawson fell in love with it at once and began the picture book's "dummy" that evening. "We all knew we had something hot," Mrs. Margaret Leaf recalls in her home in Garrett Park, Md. Because Leaf already had the second children's book in production at his own house, his wife, a buyer for Brentano's, suggested it be submitted to the Viking Press. Although it was quickly signed up with only minor revisions, the publishers were only mildly enthusiastic about it. Civil war had broken out in Spain, and they considered holding back publication. The first printing was a conservative 5,200 copies, and all of Viking's juvenile advertising budget that year was committed to William Pe'ne du Bois' Giant Otto. "Ferdinand is a nice little book," the president of the company explained, "but Giant Otto will live forever."

When it was published on September 11, 1936, the reviews of Ferdinand were unmemorable, and the book just slipped past Christmas. Then something remarkable happened. After the holidays, as other juvenile titles were being returned, the sales of Ferdinand suddenly jumped to 100 copies one week, 200 the next, and then climbed steadily, so that by 1938 it was selling 3,000 copies a week. Adults had discovered Ferdinand. Not only were they purchasing the children's book themselves, they were also passing this simple fable of a peaceable Spanish bull on to their friends. By December, Ferdinand knocked Gone With The Wind off the top of the best-seller lists. "It was a complete mystery to us," Mrs. Leaf admits, "how in the world it happened!"

The story's meaning was apparently just as mysterious. Many were convinced it was a political tract. Everyone from Franklin D. Roosevelt to Stalin was caricatured in the papers as the passive bull. Others said that the book was anti-Franco, that it was pro-Franco. Over the years, Ferdinand has been called a fascist and a communist, an anarchist and a pacifist. Psychoanalysts have judged him manic-depressive, schizoid, latently homosexual. When The Cleveland Plain Dealer accused the book of corrupting the youth of America, The New York Times replied, "There are those who love Ferdinand for his own sake, and don't care whether he is a Nazi or a Communist, so long as he is true to himself." Among these was Munro Leaf himself. "It was propaganda all right," the author said at the time, "but propaganda for laughter only." He insisted that laughter was "one of the greatest forces in the world today . . . If the book fails to make you chuckle there is no excuse for its existence, as far as I'm concerned."

FERDINAND'S distinguished admirers included H.G. Wells, Thomas Mann and Gandhi. President Roosevelt requested a copy be sent to the White House. At the annual Newbery Award dinner, Eleanor Roosevelt was the guest speaker, and she apologized for being unfamiliar with that year's winner, Ruth Sawyer's Roller Skates; the only children's book she had read recently was Ferdinand. In Nazi Germany, Hitler burned the translation for being "degenerate democratic propaganda." When Berlin fell in 1945, 30,000 copies were immediately printed and freely distributed among the children in a mission of peace. In its 50 years, it has been translated into 60 languages and is said to have sold at least 2.5 million copies world-wide. It has been pirated -- and rewritten -- in the Soviet Union. It was the only American children's book available in Stalinist Poland, and a square in Warsaw has been renamed "Ferdinand." It remained banned in Spain until Franco's death. Once the book was published there, its acceptance was acknowledged as proof that peace had finally come to that troubled country. It is no wonder that from time to time there was an international call for Munro Leaf and Robert Lawson to receive the Nobel Peace Prize.

Children, of course, are not concerned with politics, and they are the ones responsible for the book's survival these past 50 years. The Story of Ferdinand is a perfect marriage of story and art, perhaps the best modern picture book next to Wanda Ga'g's Millions of Cats. In Lawson, Leaf found his Tenniel, his Ernest Shepard. Lawson was not only a deft draftsman but also a master of characterization and picture-book pacing. Each figure is individualized, each spread a new surprise as Lawson expanded the understated humor of Leaf's tale through the beautiful and hilarious pictures. These contain countless small, witty details (such as Ferdinand's growth chart, the patches on the other bulls and those on the vain Matador's stockings, Ferdinand's whimsical cork tree) which fascinate young readers. It is no wonder that Walt Disney for once did not wander far from Lawson's original drawings when he adapted the book for animation in 1939.

Leaf's little lesson is as true today as it was during the Spanish Civil War. Like the Cowardly Lion in The Wizard of Oz, Ferdinand the Bull is not what others expect him to be. He is a social misfit who refuses to go against his nature. Like Melville's Bartleby the Scrivener, Leaf's Ferdinand just prefers not to. Every child knows what it is like to be forced to do something that he or she just does not want to do. Another writer would have clumsily transformed timid Ferdinand into a hero of the bullring. But Leaf knew that true courage is being true to one's self, no matter what anyone else might say. And it is within himself that Ferdiand finds true happiness. Happy Birthday, Ferdinand!

Michael Patrick Hearn is working on a full-length biography of L. Frank Baum.