This is an excellent question. One aspect of literature in which Saki excels is the surprise ending, and this short story is certainly no exception. Saki employs situational irony to devastating effect, letting his two main characters experience a shocking reversal of fortunes, completely the opposite of what we have been led to expect as readers.
Let us consider how he achieves this. We are presented with two sworn enemies who, perhaps rather ironically, are trapped together under the same tree. As each waits for their henchmen to arrive and cut them lose, they begin to tell the other what will happen:
"When my men come to release us, you will wish, perhaps, that you were in a better plight than caught poaching on a neighbour's land, shame on you."
However, the close proximity they are forced into and their shared fate leads them to resolve their differences and strike up a surprising friendship. We, as readers, all want a happy ending to a conflict such as this, and we join in with Ulrich and Georg as they begin to dream of how they can show each other that their overtures of friendship are real:
For a space both men were silent, turning over in their minds the wonderful changes that this dramatic reconciliation would brig about. In this cold, gloomy forest, with the wind tearing in fitful gusts through the naked branches and whistling round the tree trunks, they lay and waited for the help that would now bring release and succour to both parties. And each prayed a private prayer that his men might be the first to arrive, so that he might be the first to show honourable attention to the enemy that had become a friend.
Of course, this heightens our expectation as readers as we wait to see whose men will come first and we begin to dream likewise of the happy ending. Note how Saki deliberately plays with us by letting the two men hear sounds that they conclude are a group of men searching for them. Thus they shout out and Ulrich even gives a "joyful" cry when he sees figures approaching, and then shares other information "gladly." It is only in the last few lines that Saki hits us with the full force of the situational irony as we realise that it is not men, but a pack of wolves who are coming to "help" the defenceless men.