Star Trek: 12 Biggest Losses Starfleet Ever Faced

This devastating attack, believed initially to be orchestrated entirely by malfunctioning synthetics, saw both the destruction of the surface of the planet Mars and the Utopia Planitia Shipyards, along with the deaths of over 92,000 people.

The attack was in fact planned by the Romulan Zhat Vash, a highly secret faction of the Tal Shiar. Their sole mission was to exterminate all synthetic life in the galaxy, no matter the cost. The fleet that was being built on Mars was designed to save the Romulan Empire from the supernova that threatened to engulf it. The destruction of the fleet ensured that millions of Romulans died.

It also led to the departure of Admiral Picard from Starfleet - another huge loss for the once proud organisation.