Battle of Betazed

The Battle of Betazed was a surprise Dominion offensive against the Federation member world of Betazed during the Dominion War in 2374. It was an unmitigated disaster for the Federation and its allies, plunging the war into its darkest hour.

The Battle
The Jem'Hadar had secretly assembled a large invasion force in the Kalandra sector, which Starfleet had believed was too far from Dominion territory to represent a major threat. At the same time, the Tenth Fleet was caught out of position at the start of the invasion during a training exercise. The disadvantage was compounded by the relative weakness of Betazed's antiquated and undermanned defenses.

Ultimately, the Dominion conquered the planet and its outlying colonies in only ten hours – a humiliating defeat for the Federation.

On a strategic level, the defeat had even worse implications. With Betazed under its control, the Dominion was positioned within striking distance of the very heart of Federation territory, including such core member words as Andor, Tellar, Vulcan, and Earth itself. 

Aftermath
Several weeks later, the Dominion attempted to form a supply line running from Betazed to the Argolis Cluster, hoping to eventually launch an attack on Vulcan. 

Later that year, the Second Fleet launched at least three attacks against the Dominion positions on the planet, but the continual Dominion reinforcements and the fortification of the planet stopped them from succeeding. 

Apocrypha
In Tales of the Dominion War, the short story "The Ceremony of Innocence is Drowned" tells of what Lwaxana Troi was doing up to the battle and invasion, including mentioning the unfortunate yet heroic death of Mister Homn.

The story is continued in The Battle of Betazed, a novel that tells of the fight to recapture Betazed from the Dominion in detail. Elias Vaughn, Deep Space 9's new first officer in the Star Trek: Deep Space Nine relaunch novels, is instrumental in helping the USS Enterprise (NCC-1701-E) crew retake the planet.

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