Temporal incursion
From Memory Alpha, the free Star Trek reference
A temporal incursion is a deliberate action which creates an alternate timeline.
The Krenim weapon ship, constructed by Annorax, accomplished temporal incursions by pushing a target, anything from a molecule to a civilization, out of the space-time continuum. This essentially erases the target from history, changing the timeline to one in which it had never existed.
Numerous incursions can create turbulence in the timeline. This can make time-travel very dangerous. (ENT: "Storm Front")
Careful calculations need to be performed prior to such an incursion, as every interaction between the target and its surroundings over its entire history must be considered. Erasing something as simple as a rogue comet in USS Voyager's path, as Chakotay had suggested, would have eliminated 8,000 civilizations in a radius of 50 light years, because fragments from that comet had seeded life in the sector billions of years ago. Indeed, Annorax was never able to achieve his goal of fully restoring the Krenim Imperium despite hundreds of temporal incursions. Ultimatly all of his temporal incursions were erased and his goal of restoring his wife was completed when Captain Janeway destroyed the Temporal Weapons Ship and erased it from history by ramming Voyager into it. (VOY: "Year of Hell", "Year of Hell, Part II")
According to the records of the 29th century timeship USS Relativity, the USS Voyager had been involved in three major temporal incursions, all of which had to be repaired by Captain Braxton. The mission by Seven of Nine to prevent a temporal disruptor from destroying Voyager also caused a number of temporal incursions in various time frames, which were ultimately eliminated from the Relativity with an incursion factor of .0036. (VOY: "Relativity")
Multiple temporal incursions were made throughout the Temporal Cold War. For example, the Sphere Builders sent three Xindi-Reptilians to Detroit, Michigan, Earth, 2004. Daniels' faction had detected this. Apparently, it takes time for an incursion to reach the future. (ENT: "Carpenter Street")
