The Promethean Empire had attempted to invade Terra once before, but their plans were foiled by the Grand Alliance, Compact, and Coalition, who all evicted the Promethean forces from the system.
The Prometheans, having recovered from their defeat so many years ago, now set out to exact revenge on the weakened Coalition and Compact, as well as Humanity. A small fleet of twelve ships entered the Sol system in January of 1973 and set up offensive positions near Venus.
Several Grand Alliance ships remained in the system despite the wishes of the Humans themselves. These ships had yet to leave the system for the Seventh Galactic War, and were ordered to remain in the system should some calamity fall upon the fragile Human civilization.
The Humans were expecting the Prometheans to return one day, and had sent their small fleet of fourteen ships to intercept the Prometheans when they were detected to have passed the Kuiper Belt. This move was criticized, however, by some who argued that a battle in Terran orbit would allow the Humans to deploy more assets against the invaders, such as international planet-to-space missiles (PSMs), the Soviet Union's space station, and the United States' lunar military base.
This was countered with the idea that allowing the Prometheans into Terran orbit could enthreaten Human cities. This was considered more important, and as such all possible Human ships were deployed to Venus to intercept.
A third of the Grand Alliance fleet accompanied the Humans when they too noticed that the Prometheans had entered the system, adding another five ships to the total.
Human-Alliance ships reached Venus first and set up defensive formations. When the Prometheans arrived, the Alliance ships opened fire, distracting the Prometheans while the Human ships circumvented the enemy armada.
Human ships adeptly dodged most Promethean fire, as only a few were energy shielded, and those that were had weak shields. When the Human ships had flanked the Prometheans, they opened fire. The combined fire took out most of the Promethean fleet, and the remaining four ships struck their colors shortly.
The Grand Alliance suffered one damaged ship, while the Humans lost two scout ships and had three damaged sloops.
The battle was heralded as a great victory by a fledgling Humanity, as Humans had reached into the stars and beat the Prometheans where Humans were at their weakest, in space. This also caused some more pan-Humanism and nationalist sentiments back on Earth, with some suggesting what Humanity could do when united.
Such nationalism reached its height a week later, when the United Nations symbolically declared the entire inner solar system to be Human territory, followed by a resolution encouraging Human colonization of the entire solar system.
The resurgent Prometheans were soon defeated by the Grand Alliance a month later, but the distraction cost the Alliance as the Compact took advantage of this. The Promethean Empire became a vassal state of the Dravimosians soon after. Because of the victory and the ongoing war, two-thirds of the Alliance fleet withdrew from the system.