|Centuries:||23rd Century||24th Century||25th Century|
- 15: Hundreds of Borg cubes invade the Alpha and Beta quadrants at multiple points without warning. Dozens of Starfleet vessels are lost within hours of the beginning of the Borg War.
- 19: After discovering that the Borg are entering the quadrant at the Azure Nebula and attacking various worlds from there, the Federation, the Klingon Empire, and several smaller powers sends every starship available to combat the threat. The ensuing battle is a disastrous defeat, and several hundred starships are lost, more than were destroyed in both the Federation and Klingon fleets in the Second Federation-Klingon War and the Dominion War combined.
- 20: Deneva is assimilated by the Borg.
- 21: Risa is assimilated.
- 23: The starships Enterprise, Titan, and Aventine succeed in making first contact with the Caeliar, an advanced and isolationist species that inadvertently created the Borg. The Caeliar destroy the Borg Collective and welcome all former-Borg individuals into their Gesalt (group mind), and then disappear, leaving behind no remaining Borg.
- 5: Starfleet issues General Order 65, requiring all Starfleet personnel to secure any abandoned Borg technology they discover.
- 2: Mu Arae joins the United Federation of Planets.
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