How does Saki develop the central idea of friendship and revenge in "The Interlopers"?
The feud between the families of the von Gradwitzes and Znaeyms began with a lawsuit in the days of the grandfathers of Ulrich and Georg, but the animosity and ill will between the two young men is exacerbated by Ulrich von Gradwitz's strong hatred for Georg Znaeym. It is only an act of Nature that brings them together.
Because of this ill will, Ulrich goes into the forest where there is "a disturbing element," and he comes face-to-face with his enemy. A force of nature brings a huge beech tree's limbs down upon them, leaving the two men pinioned beneath it. At first, they curse each other and boast that each one's men will arrive before the other's and revenge will be served. As they wait to be rescued and their discomfort increases, Ulrich reconsiders his feelings. The wine in his flask is warming, so he offers it in a gesture of friendship to the other man, Georg Znaeym: "Let us drink, even if tonight one of us dies." At first, Georg rejects this offer from an enemy." As they lie in pain, though, the two men reconsider what is important in life. Ulrich says to Georg,
I've come to think we've been rather fools; there are better things in life than getting the better of a boundary dispute. Neighbor, if you will help me to bury the old quarrel, I—I will ask you to be my friend.
After some thought, Georg speaks in reconciliation,
What peace there would be among the forester folk if we ended our feud tonight. . . Ulrich von Gradwitz, I will be your friend.
Then, in a gesture of true friendship, each man offers to have his men help the other if they arrive first.