From The Art and Popular Culture Encyclopedia
Bellona was an Ancient Roman war goddess. She is believed to be one of the numinous gods of the Romans (without a particular mythology and possibly of Etruscan origin), and is supposed by many to have been the Romans' original war deity, predating the identification of Mars with Ares. She accompanied Mars into battle and is taken variously as his sister, wife or daughter. She is also (as at her temple in Ostia) syncretized with Magna Mater.
Bellona's attribute is not a sword and she is depicted wearing a helmet and armed with a spear and a torch.
Bellona's festival was celebrated on June 3.
The name "Bellona" derived from the Latin word for "war" (bellum), and is directly related to the modern English word "belligerent" (lit., "war-waging"). In earlier times she was called Duellona, the name being derived from a more ancient word for "war".
In art, she is portrayed with a helmet, sword, spear, and torch.
Ammianus Marcellinus, in describing the Roman defeat at the Battle of Adrianople refers to "Bellona, blowing her mournful trumpet, was raging more fiercely than usual, to inflict disaster on the Romans".
In later culture
Near the beginning of Shakespeare's Macbeth (I.ii.54), Macbeth is introduced as a violent and brave warrior when the Thane of Ross calls him "Bellona's bridegroom" (ie Mars). The goddess has also proved popular in post-Renaissance art as a female embodiment of military virtue, or a good opportunity to portray a woman in armour and helmet.
Also, the "Temple of Bellona" was a popular choice of name for the small mock-temples that were a popular feature of eighteenth and nineteenth century English landscaped gardens (eg William Chambers's 1760 Temple of Bellona for Kew Gardens, a small Doric temple with a four-column facade to contain plaques honouring those who served in the Seven Years War of 1756-64).