P.G. Wodehouse vs. A.A. Milne.
At the Paris Review:
The two men were initially friends: exactly the same age, and both comic writers, they moved in the same circles in 1920s London, playing on the same cricket team and contributing to many of the same publications. In 1928, they even collaborated on the adaptation of Wodehouse’s A Damsel in Distress. By the 1930s, their friendship had cooled somewhat—Wodehouse defenders cite jealousy—but it wasn’t until World War II that things became actively hostile.