The Battle of Janjur Qom was a brief conflict between the San’shyuum and Forerunners on the quarantined San’shyuum homeworld of Janjur Qom several years prior to the firing of the Halo Array during the Great Purification in 97,445 BCE. Towards the end of the Human-Forerunner Wars, the San’shyuum, who had been allied with humanity for much of the conflict, betrayed the alliance in exchange for leniency from the Forerunner empire. When the Forerunners emerged victorious, they quarantined all the San’shyuum to their home system including Janjur Qom, a much less harsh punishment than the one given to the humans.
The quarantine remained in effect for thousands of years, with the San’shyuum slowly rebuilding and secretly storing weapons in case they were ever needed. When the Librarian arrived on Janjur Qom to index their species towards the end of the Forerunner-Flood War, the San’shyuum suspected something was wrong and rebelled. Even using the hidden weapons caches on the planet, however, they were no match for the Forerunners, who sent an entire fleet to deal with the San’shyuum. The Master Builder, who still wielded a great deal of power at this time, elected to not just put down the rebellion, however, but brought in a halo, Installation 07, and fired it, wiping out any and all remaining San’shyuum in the entire system.