The 2381 crisis in which former cadet Nick Locarno gathered disaffected crews into a rogue fleet and threatened to use a Genesis Device.
For much of 2381 a mysterious ship attacked vessels belonging to the Klingons, the Ferengi and other powers. Each attack was planned by a low-ranking member of the target ship's own crew. The mastermind was Nicholas Locarno, who had been expelled from Starfleet Academy decades earlier after a fatal training accident.
Locarno recruited these mutinous crews into a new fleet and demanded recognition, threatening to set off a Genesis Device if he did not get it. He kidnapped Beckett Mariner, thinking her own frustrations with Starfleet would make her an ally. Instead she warned everyone not to trust him and tried to escape with the device.
Captain Freeman disobeyed orders and went to rescue her daughter in an inoperable battleship, provided by the Orion D'Erika Tendi. With Boimler as acting captain, the Cerritos used its tractor beam to crash the battleship into Locarno's shields. Mariner armed the device and pleaded with Locarno to let go of his anger, but he refused. Freeman beamed her away, and the device turned Locarno and the surrounding matter into a new planet, which Starfleet named Locarno.