The Battle of Antares was a space fleet battle between the Sontaran and Rutan Empires. It took place in the Antares system in 2371. It was the culmination of a long-term Sontaran plan to gain a foothold in the former Tzun Empire and access its rich sources of Terullian. The Tzun were long extinct by this time.
The battle was never supposed to take place. The plan called for the Sontarans to slowly tag the human population of the nearby colony of Raghi in the Unukalhai system with a polymerase chain via a retro-virus in the colony's water supply. Meanwhile, another Sontaran operation was taking place elsewhere in the star system. A small Sontaran unit had captured the human outpost on Agni, one of the moons of the gas giant Indra. The humans were hypnotised and used as slave labour to conduct repairs on a damaged Tzun Stormblade, particularly on its graviton drive.
Once both of these initiatives were completed, a Sontaran task force under the command of Fleet Marshal Stentor would lay in wait for the Rutans. When Rutan probes arrived, they would detect the polymerase chain tags on the humans of Raghi. The Rutan fleet at Antares would be mobilised to destroy what they believed a Sontaran base. Upon arriving in-system, the Stormblade's graviton drive would condense Indra's atmosphere, achieving nucleosynthesis and creating a miniature star, wiping out the Rutan fleet. The Sontaran fleet would then move against the unprotected Antares, siphon off their data cores from orbit and destroy the base via orbital bombardment. The Sontarans would be free to move into the Terullian-rich sector at their leisure.
The operation did not go off as planned. The Fifth Doctor sabotaged some of the Sontarans' plans at Agni and also at Raghi and the Doctor's allies managed to destroy the aforementioned Tzun Stormblade, but the Sontarans were able to capture the Doctor's TARDIS and secure it aboard their flagship, a Linx class cruiser. The Sontarans did not know that the Tzun vessel had been destroyed, and continued with their operation.
The Doctor contacted the Rutan probe when it arrived in the Unukalhai system, and warned them of the Sontaran plan. The Rutans decided to surprise the Sontaran task force by leaving the Antares system, jumping back shortly thereafter. The Doctor offered to accompany them in a human ship, and, using a stolen Sontaran transponder code, would board the flagship and lower its shields. The Rutans, suspecting that the Time Lord was after his TARDIS, announced that they would accompany him.
When the Sontaran probes detected build-ups in the drive systems of the Rutan vessels and intercepted communications verifying a hyperspace jump to Unukalhai, the Sontaran task force jumped to Antares. At first, they detected no vessels of consequence. Then Rutan vessels began dropping out of hyperspace around the fleet.
Despite this, exemplary admiralship by Stentor allowed the Sontarans to hold their own for a while. The Sontaran fleet destroyed many Rutan ships, but lost many vessels. A battle of attrition was fought. In the midst of the chaos of battle, the Intelligence section aboard the Linx-class cruiser decrpyted an important Rutan transmission. It detailed the location of the Rutan queen. Stentor immediately re-prioritised and ordered that the information be downloaded to every vessel in the fleet capable of carrying the data, in hopes that some of them would return to Sontaran space with the intelligence.
This forced Karne, a Rutan spy who had infiltrated the Fleet Marshal's staff, to reveal himself. He killed the Fleet Marshal, escaped the bridge and sabotaged the ships reactors. With operational failure looming, General Skelp took command and ordered the Linx-class cruiser to ram the Rutan base on Antares. The cruiser exploded, destroying the base and most of the rest of both fleets. A few Sontaran Goban class III gunships survived to escape. The Rutan fleet was completely destroyed.
The war ended in a tactical draw with the Sontarans achieving a strategic victory. Though the Rutan fleet and the base on Antares were destroyed, there were no Sontaran ships of any significance to exploit this advantage. They could not follow up and exploit the Terullian resources of the extinct Tzun Empire, which was the entire point of the operation. However, acquiring the intelligence regarding the Rutan queen was incredibly valuable. There was an immediate re-prioritisation on the Sontarans' part after the intel reached the Grand Strategic Council. (PROSE: Lords of the Storm)