They have never shown the second ogres war. Granny just mentions it in Red Handed. She just mentions that that is when she lost her brothers. The first ogres war is the one when Rumpel was still a human and then he became the dark one, then we finally saw him end it in this episode. I agree that the duke was keeping it going to control the people.
No one has ever called what happened with Belle or with Emma/Snow in Season 2 to be an ogres war. They could just be skirmishes and not full on wars that last years.
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