There were two Bellonas in Rome and they had almost nothing to do with each other. One was an old Latin war-power whose temple functioned as an annexe of the Senate. The other was an Anatolian goddess whose priests slashed their own arms in the street. Roman writers used one name for both, and modern summaries that blend them produce a goddess who never existed.
Duellona: the name is a sound-change
Her older form is Duellona, and duellum is the archaic form of bellum, war. The shift is regular in Latin — duonus becomes bonus, duis becomes bis — so her name is simply "the war one", formed from a noun rather than inherited as a personal name. That places her among the Roman functional deities: a power named after the activity, like Victoria or Concordia, rather than a character with a biography.
Her relationship to Mars is unstable across the sources, which is what you would expect of a personified function retrofitted into a family. She is called his sister, his wife, his daughter and his charioteer by different Latin authors, and the Roman family tree accordingly attaches her loosely.
A temple used as a committee room
Her temple was vowed in 296 BCE by Appius Claudius Caecus — the blind censor who built the Appian Way and the first Roman whose speeches were still being read centuries later — during fighting against the Etruscans and Samnites. He put it in the Circus Flaminius, outside the sacred boundary, and that location made it an institution.
Because a general holding military command could not enter the pomerium without laying that command down, and because a general seeking a triumph needed to keep it, the Senate met him here. Foreign ambassadors from enemy states, who were not admitted into the city, were received here. Debates on whether to award a triumph happened here. Bellona's temple is where Rome conducted the business of war with people it could not let indoors.
Throwing a spear at a symbolic country
In front of it stood the columna bellica, a small column with a patch of ground beside it that was legally designated as enemy territory. The old procedure for declaring war required a fetial priest to travel to the enemy's frontier and hurl a spear across it. Once Rome's enemies were months away by sea, that became impossible, so the column was used instead: the spear was thrown from Roman soil over the column onto the notional foreign ground, and the declaration was complete.
This is Roman legal fiction at its most naked, and Romans knew it. Cassius Dio reports that the rite was performed by Octavian in 32 BCE for the declaration of war on Cleopatra — a war against a foreign queen rather than a Roman rival, which was the whole point of the presentation — and it was still being revived by emperors two centuries later. A ritual that had been rendered obsolete by success was kept because performing it correctly was what made the war just.
Ma of Comana, and the arms cut open
The second Bellona arrived from Cappadocia. Ma, the goddess of the great temple-state at Comana, was brought to Rome in Sulla's time — the tradition is that she appeared to him in a dream and handed him a thunderbolt — and her name was rendered as Bellona because both were warlike.
Her cult looked nothing like Roman practice. Her priests, the bellonarii, processed in black robes to the noise of trumpets and drums, worked themselves into a frenzy and cut their own arms and thighs, offering the blood and, according to several accounts, drinking or sprinkling it. They prophesied while in that state. Juvenal, Tibullus, Lucan and Martial all mention them, uniformly as a spectacle of foreign fanaticism, in the same register Romans reserved for the self-castrating priests of the Great Mother.
Rome's usual solution to such cults was containment rather than prohibition: license the worship, keep Roman citizens out of the more extreme roles, and let the foreign priesthood run it. The literary disgust and the official tolerance coexisted for centuries.
Why Enyo is not a real equivalent
Greek Enyo is the standard equation, and it is thin: a battle-companion of Ares with few cults and less mythology. Nothing in Greece corresponds to Bellona's temple as an extramural Senate chamber or to the spear-and-column procedure. This is one of the clearest cases on the site where interpretatio graeca supplies a label and nothing else, and where the Roman figure's real content is entirely institutional.
Where her root ended up
Bellona's own name did not travel far, but the noun behind it went everywhere. Bellum gives English belligerent, bellicose, antebellum and casus belli, along with rebellion by way of rebellare. The goddess herself resurfaces as the name of Royal Navy ships across three centuries, as Rembrandt's armoured 1633 portrait, as the ruined city in Samuel Delany's Dhalgren, and as a playable character in more than one modern game — most of which give her the frenzied Cappadocian character rather than the Roman committee-room one.
Points worth pinning down about Bellona
Did women serve her?
The Cappadocian cult had priestesses as well as priests, and inscriptions record women in her service. The older Latin Bellona's temple was administered in the ordinary Roman way, through magistrates and attendants, and there is no attested priesthood restricted to her comparable to the flamines of the archaic gods — another sign that her cult is a Republican foundation rather than an inheritance from the earliest layer.
Was the spear-throwing rite ever used against Romans?
Not properly. The fetial procedure existed to establish that a war was iustum, justly declared against a foreign enemy, which is exactly why it could not be applied to civil war — and why Octavian took such trouble to declare war on Cleopatra rather than on Antony. Roman civil wars were fought without the rite, and the awkwardness of that is visible throughout the literature of the first century BCE.
Is her temple visible today?
Its remains lie under later construction near the Theatre of Marcellus, and its position is known chiefly from the fragmentary marble city plan of Rome, the Forma Urbis, and from the topographical sources. The Circus Flaminius area was heavily built over from antiquity onward, so what survives is mostly documentary.
Why is a "goddess of war" separate from Mars at all?
Because Rome routinely gave separate cult to the abstracted aspects of an activity rather than folding them into one deity: Victory, Concord, Peace, Fear and Pallor all had altars or temples. Mars is a god with a wide agricultural and ancestral portfolio; Bellona is the fact of warfare itself, and specifically its declaration. Roman religion was comfortable worshipping both the person and the process.