Operation: Ragnarok
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In an alternate timeline, Operation: Ragnarok was put into place after the appearance of the first Doomsday Weapon and the destruction of the USS Enterprise. It ordered all exploratory missions cancelled and the entire Starfleet to instead fight off the duplicating army of machines. The operation became colloquially known as the Doomsday War. (Star Trek: New Voyages: "In Harm's Way")
