Skyllian War

The Skyllian War was a major interstellar conflict fought between the and the. It officially took place from 2217 to 2237, lasting for twenty years, but hostilities lasted until 2240 which added up to twenty-three years of fighting.

Overview
and have been at odds with one another ever since the Systems Alliance settlements began to appear in the, a region of space in which the batarians sought full-control of. This tension existed for many decades, gradually intensifying with every action that they perpetrated against one another until it inevitably spilled over into all-out war. The Skyllian War was viewed as an unavoidable conflict by the majority of the galaxy as, even after the arrival of the Reapers, the batarians still held a great deal of animosity towards humanity for the Alpha Relay catastrophe.

Beginning
In 2185 CE, a disastrous event occurred in which the Bahak system's mass relay was destroyed, taking more than 300,000 batarian lives with it. While it was originally believed to be an accident of some kind, it became evident that the had something to do with the disaster after further investigation led back to  and an unknown but high-ranking Alliance official.

The Alliance claimed that Shepard defected to and were in the process of administering punishment, however, the Hegemony believed that Shepard was acting as a  and that the Alliance was attempting to cover their tracks as they had done before with other agents.

Despite the Alliance's claims of innocence, the Hegemony had already begun preparations to launch a full-scale retaliation. Before the batarians could muster enough of their forces to declare war on the Alliance, the would arrive and put a strain on the entire galaxy. The batarians lost atleast four billion more lives and 90% of their military force in the incursion, leaving the Hegemony in a state of near-collapse. The Hegemony still planned to avenge the lives lost in the bahak system, however, so they quickly prepared once again with most of their reconstruction efforts going towards the military.

It wasn't until 2217, more than 30 years in the future, that the batarians would manage to build up their military and develop counter-strategies to Alliance military tactics. In a surprise move by the Hegemony, the batarians declared war for an atrosity committed against them three decades ago that went unanswered. In, the batarians deployed an armada of warships under the command of Commandant Ran'serah to attack an Alliance orbital platform array over Ragel. It was a brutal assault that resulted in the loss of 4,500 Alliance naval personnel and brought about a fierce retaliation by Alliance forces.

In July of the same year, Admiral Foster led Fourth Fleet in a campaign against Hegemony forces which led to the largest battle of the year. After a series of skirmishes against batarian flotillas that stretched for months, Foster led his fleet in an incursion of Tanok -- a batarian-controlled world on the borders separating the batarian and human territories. This engagement, known as the First Battle of Tanok, was a drawn-out battle that ultimately led to the Alliance gaining control over the lightly-defended planet but the batarians were not shaken by the defeat. In fact, they were preparing to carry out the war for as long as possible.