Possible the Duke wanted the war to go on. Possible the Duke asked the Dark One to make him win the war, but that was not doable even with the darkest powerful magic in this world, and only a truce was the way out, but that was something not coming to the mind of the Duke, so he never asked for it. Rumple as The Dark One didn’t care what the Duke wanted, so he ended the fightings by making a truce.
Wars are always coming with propaganda. Maybe the ogres originally were men, maybe not. One way or the other the common image, the image spread among humans about ogres was influenced by war propaganda. We know pretty much nothing about them, their way of living, their culture, their abilities, we know only what has been told by humans. Remember what has been said about the giants. Think the ogres could be the “savages” of the Enchanted Forest, no one knows much about them and no one knows how to communicate with them, but everybody fears them because they are physically stronger than humans. Or they are just bad guys like the trolls (although we only met these bridge trolls, bandits, who knows if all trolls are like that).
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