What is unexpected and ironic about the ending is that the men are fighting each other, but they both end up fighting wolves. This is situational irony.
“The Interlopers” is a fable about two men who are battling with each other. Ulrich von Gradwitz and Georg Znaeym are neighbors who are feuding because of some long-standing conflict between their families over a land dispute. One night they are both roaming the forest hoping to “run into” the other accidentally so they can shoot him. They run into each other all right.
When the wind blows a tree down, Georg gets trapped under the tree, which Ulrich thinks is funny.
“So you’re not killed, as you ought to be, but you’re caught, anyway,” he cried, “caught fast. Ho, what a jest, Ulrich von Gradwitz snared in his stolen forest. There’s real justice for you!”
Unfortunately, Georg is not the only one trapped under the tree. Ulrich is too! He is being rather short-sided about the whole thing, actually. So the two men share insults for a while, not really trying to get out. They are more concerned about hating each other than about trying to get out. There is really nothing they can do. Each man is so full of righteous indignation, vindicated by the fact that he is right, and the other is wrong, that they do not realize that there is someone coming. Then they think they are being rescued, and each thinks it is his own men. They each think they are the ones in the right. It turns out to be wolves.
The irony, of course, is that if they had worked together, they probably could have lifted the log off together, since they were both trapped under it. They could have freed themselves and left, and fought off the wolves together. Instead, they died—together.
There are three types of irony. These are verbal irony, situational irony, and dramatic irony. This is situational irony, which means that the event is the opposite of what you thought would happen (probably that one would kill the other). Dramatic irony is when the reader knows something the characters don’t, and verbal irony is when there is some wordplay (like jumbo shrimp). The fact that what you expected to happen, that the men would kill each other, was the opposite of what actually happened, that wolves killed them, makes it dramatic irony.