The empire used the Ultima Bomb enhanced by the Secundus l'Cie Qun'mi's powers to obliterate the Lorican Alliance in an operation dubbed "Operation Northern Dawn". The bomb was deployed by Brionac, the empire's experimental magitek armor developed as part of the empire's Ultima Bomb Project. Once Cid Aulstyne ordered the construction of a new magitek armor that could transport and deploy Ultima Bombs, engineers from all over the country flocked to the Steelworks in hopes of lending their talents to this national cause.
The Brionac could load a total of eight Ultima Bombs at a time and fire them halfway across Orience. Its range did not extend far enough to strike the Dominion of Rubrum and Kingdom of Concordia capitals without crossing their borders, however, so scientists began brainstorming. They decided to outfit the mech with heavy plated armor and magic barriers to ease the difficulty of invasion.
Claes Celestia Misca Sancest, an ambassador of the Azure Dragon Crystal and the l'Cie Queen Andoria, travels to Akademeia to speak with its chancellor, despite the l'Cie's tendency to not meddle in the affairs of mortals. As she arrives in Akademeia, students speculate the Ultima Bomb destroying Lorican Alliance was her motivation. Fear spreads among the populace, some afraid the Ultima Bomb could destroy all of Orience and that the end times, Tempus Finis, loom near.
Imperial hopes are dashed when a dominion task force infiltrates the arms production facility and demolishes the Brionac prototype in its unfinished state, leaving the empire without a means of deploying the Ultima Bomb. The empire fights the rest of the war without the bomb's aid but the tide of battle turns when the Vermilion Bird Crystal's Secundus l'Cie Lady Caetuna summons a Verboten Eidolon to obliterate the Militesi forces. The dominion rapidly conquers most of Militesi territory and as they infiltrate its capital of Ingram, general Qator Bashtar heads out to engage a dominion squad sent as reinforcements in his MA, the Gabriel.
Unknown to Bashtar, Gabriel had been fitted with a malfunctioning prototype of an Ultima Bomb by a Militesi engineer who saw the Militesi surrender inevitable, wanting to wipe out both armies. Realizing the danger, Qator flies Gabriel into the atmosphere and jettisons the bomb as it is about to detonate. The Ultima Bomb explodes in the atmosphere, destroying Gabriel and Bashtar, but the Militesi city is saved. When Cid Aulstyne hears the news of an Ultima Bomb exploding in the atmosphere, he realizes Bashtar perished in the blast.
Ultima means "the last" in Latin and many Latin-based languages. In the Spanish versions of many Final Fantasy games, it is written as "Artema," a close transliteration of the Japanese katakana.
The name likely refers to the spell Ultima, a recurring magic in the series and commonly the most powerful one in a game. How it is used through a physical conduit by technology makes it similar to the real world weapons of nuclear warheads; its existence as the first of its kind, and in a time of war makes it similar to the weapon of the atomic bomb used in World War II.
Within the game's lore, the name may refer to the Ultima War, waged before the peristylia had yet been established between four sovereign nations that each took it upon itself to create the mightiest army the world had ever known, and when the time came, all four rode forth to wage the war to end all wars—the Ultima War. The Annals of Orience posit that while the tale has seen its fair share of embellishments and alterations, the name of the war, "Ultima," remains consistent.
- Concept art for an imperial cannon that operates on a similar mechanism as the Ultima Bomb exists, but was not used for the game.