The Callisto Incident was a series of events involving the UNSC Callisto that is considered the first true insurrectionist attack from January to March 2494. In January, the UNSC Callisto involved in an incident during the inspection of a trading vessel for contraband slipspace engine materials, resulting in the exchange of gunfire and the death of twenty-seven merchants and three UNSC personnel. The following month, the Callisto was performing similar inspection actions when a trading vessel led the ship into a trap, killed the crew, and hijacked the Callisto.
In search of the Callisto, a UNSC battlegroup consisting of the UNSC Las Vegas, Buenos Ares, and Jericho entered the system and quickly found the pirated ship on March 2nd, 2494. During the chase, the Callisto led the battlegroup into a nearby asteroid field, and used a planted trap of nuclear warheads in the field to destroy or disable the entire battlegroup. The UNSC Las Vegas was able to recover and ultimately complete the mission of recapturing the Callisto through unorthodoxed actions taken by Lieutenant Preston Cole.