|Battle of Tyburn|
|United Earth Starfleet||Romulan Star Empire|
| Captain Jonathan Archer|
| Mining base
Unidentified Earth Starfleet vessels
|65 Romulan vessels|
|Casualties and losses|
|Indeterminate|| Indeterminate number of Romulan vessels destroyed or disabled.
During the mission to Encaria on May 12th 2159, a Starfleet task force led by Enterprise managed to find and destroy the production facility for the Romulan toxin. However, one Romulan cargo ship went to warp and escaped, carrying a large quantity of the bio-agent. Following this, the Romulan Imperial Fleet began a big push into strategic Starfleet sectors, believed to be on a heading for Earth. Upon being informed of the situation by Reggie, who was based at the Tyburn mining base, Captain Archer voiced his belief that the Romulans were planning to use the toxin on Earth. By that point, the Romulans were set to enter the Tyburn sector shortly, though Starfleet had managed to intercept some elements of their fleet in Orcini.
Starfleet picked up at least thirty Romulan vessels entering the Tyburn system, though their cloaking technology made it difficult to ascertain their strength. Reggie noted to Captain Archer that all elements of the Starfleet were placed at Tyburn; if the Romulans were not stopped, there would be nothing left between their ships and Earth's solar system. (ST video game: Legacy)
Enterprise immediately changed course and warped to the Tyburn system, where they found the mining base, defended by only two Poseidon-class destroyers, under attack by five Romulan vessels consisting of four birds-of-prey and one Battlehawk-class battleship. From the mining base, Reggie reported to Archer that they were taking a severe beating. While his personnel worked to power the orbital facility's cutting beam back up, Reggie requested that Archer buy him the time they needed. Archer answered the call, though he predicted that the Romulans would eventually overrun the Tyburn system. Led by Enterprise, the fleet successfully defended the base and reinforced the Starfleet ships already fighting in the system, destroying the first group of five Romulan vessels as well as an additional three birds-of-prey. However, a total of 54 Romulan vessels, 15 birds-of-prey, 5 Battlehawk-class battleships, 8 Swiftwing-class destroyers, 12 Hathos-class vessels, and 14 Skyhawk-class destroyers, remained.
By that point, the mining base's crew had successfully powered up their cutting beam, and realigned its orbit to fire the beam into space, allowing them to defend themselves against the Romulan vanguard. Regarding the rest of the Romulan fleet, Reggie directed Captain Archer to four sensor platforms, powered by an early form of nuclear fusion, that had been deployed across the system by the Vulcan years prior. Having brought the sensor platforms back online remotely, the Tyburn base reprogrammed their command functions, configuring them to respond to a coded hailing frequency which would detonate them, resulting in a nuclear blast; Reggie and Archer anticipated that, if this was done so in proximity to the Romulan ships, the detonation would create an electromagnetic pulse which would disable the Romulans' systems, their shields unable to keep out the full electromagnetic range.
Following the detonation of a sensor platform, Enterprise detected three Romulan transports that had been decloaked while retaining their shields; Archer determined that the Romulans had distributed their remaining toxin to these ships. As found by the Tyburn station's science officer, the transports were using shield generators designed for deployment on outposts, a feat which Archer deemed impossible. Though the Starfleet vessels could not penetrate these shields, the personnel at Tyburn suggested that their cutting beam would be enough to do so. However, the beam would leech all primary energy stores; after each discharge, it would take some time to get the capacitors back up to full power for another shot. To provide an opening for the mining base, the Starfleet vessels engaged the Romulan transports, firing by aft and concentrating their fire on the engines, their weak area. Though the Starfleet vessels were unable to destroy the transports alone, they were able to slow them down by inflicting moderate damage upon their engines, leaving them temporarily dead in space and thus keeping them within the limited range of the facility, whose cutting beam ultimately destroyed all three ships one by one. (ST video game: Legacy)
Though the Romulan biogenic disseminators were destroyed, the Tyburn system was contaminated by their bio-agent. However, the Starfleet forces managed to prevent the Romulans from using their weapon on Earth, and stopped their advance deeper into their space. Captain Archer saw that work began quickly to synthesize a counter agent from the virus sample that Starfleet created, in order to help the people of the Tyburn system. Archer remained unsure as to how or why the Romulans tried what he saw as such a desperate move. Suspecting that Commander T'Uerell was involved in this incident, Archer intended to question the Vulcans about T'Uerell's work. In a personal log recorded following the battle, Archer voiced his doubt that Starfleet had heard the last of T'Uerell, and suggested that they be prepared for their next encounter. (ST video game: Legacy)