Star Trek: 12 Biggest Losses Starfleet Ever Faced
3. The Klingon War 2256 - 2257
The Klingon War of 2256 - 2257 was a divisive story-line in Star Trek Discovery, as it dominated the majority of the first season, ensuring that the optimism of Star Trek was missing from many of the episodes.
Starbase 1 is heralded as something of a last, safe space in Federation territory. Admiral Cornwell takes command of the Discovery on their return to the Prime Universe, bringing the crew up to speed. The Klingons have devastated much of Starfleet, with a third of Starfleet being lost to their forces.
The loss of Starbase 1, however, is the single greatest loss during the war. House D'Ghor invades, destroying the three support starships surrounding the station - and eliminating all eighty thousand people aboard, including much of the Starfleet Admiralty.
Peace comes to the Alpha Quadrant shortly after this, after L'Rell holds the Klingon Empire hostage with a bomb in the centre of Quo'nos.