Battle of the greater Ark

The Battle of the greater Ark was the penultimate battle in the Forerunner-Flood war, fought around the Greater Ark.

Background
The greater Ark, the original Ark installation and the primary facility of the Conservation Measure, had become the last line of defense for the Forerunner ecumene after the Forerunners were forced to abandon the galaxy itself in the face of the unstoppable Flood onslaught. However, the placement of all Forerunner governing functions, strategic command and the majority of their population as well as military forces also made it an attractive target for the Flood, which could, through a concentrated assault, deliver a crippling blow to their enemy. There was one other motivator: Omega Halo was stationed along with the Greater Ark and was a threat serious enough to warrant trapping the entire region of space in a space road "bubble".

The battle
An enormous Flood-controlled fleet coordinated by the Graveminds and the traitorous Forerunner AI Mendicant Bias, supported by numerous Precursor star roads, attacked the Greater Ark and the nearby Omega Halo, the last of the original twelve Halos, except for the modified Installation 07. Despite the Forerunners' efforts at defending the Greater Ark with their remaining military assets, their forces were quickly overwhelmed not only by the Flood's vast numerical superiority but also the power of the star roads. Although Omega Halo was fired, decimating a small portion of the star roads as well as purging the satellite galaxy of Path Kethona of sentient life, the star roads soon destroyed both the Halo and the greater Ark.

With the loss of the Greater Ark and Omega Halo's defensive systems, there was little hope for the remaining Forerunner forces under the command of Offensive Bias. While Offensive Bias put up a desperate running fight, it was hopelessly outnumbered and outclassed thanks to the near-indestructible nature of the star roads. Still, its capability was demonstrated by its managing to extricate several thousand warships from what should have been an inescapable trap.

Aftermath
The battle marked a catastrophic defeat for the Forerunners, who lost the vast majority of their remaining population, leadership, and military strength. Additionally, a large portion of the Lifeworkers' biological samples of the galaxy's species stored on the greater Ark and Omega Halo were lost; in addition to the destruction wrought by the star roads, the Ur-Didact used a Composer to harvest Omega Halo's sizable transplanted human population, severely complicating the Librarian's plans for mankind and the galaxy on the whole. The Librarian and her aide, Monitor Chakas, managed to salvage a few of the specimens; Chakas also saved a handful of Forerunners, including the IsoDidact from Omega Halo, aboard a Gargantua-class transport. Using coordinates provided by the Master Builder, Faber - killed during Omega Halo's destruction - the few survivors traveled to Installation 00, the Lesser Ark, its location still secret from the Flood, for the moment. The IsoDidact, the last legal commander of the Forerunner race, accepted that a true victory was now impossible. As such, the final Halo Array would be distributed across the galaxy by Offensive Bias and fired by the IsoDidact, killing most of the Flood and starving those that survived, ending the war.

The Battle of the Greater Ark also seems to have another effect: when Mendicant Bias attacked the portal leading to the Lesser Ark, it did not use star roads or any Precursor artifacts. Whether due to arrogance, disdain, overwhelming rage, or a simple desire for a "personal" kill, this omission would enable Mendicant's defeat by the "inferior metarch", Offensive Bias.

List of appearances

 * Halo: Silentium