Elephants carrying castles were popular symbols in Mediaeval and Renaissance art. They stood for both strength and restraint, and often referred to ancient history, in particular Hannibal’s famous use of Elephants to invade the Italian peninsular. The Bomarzo elephant is a curious instance of this tradition, especially so since it holds a presumably wounded or dead Roman soldier in its trunk, who in turn holds an unidentified object loosely in his right hand. According to Lang (1957), this elephant and castle refers to a biblical story, that of Eleazar in The Book of Maccabees. Eleazar slays the elephant of King Antiochus V Eupator, but is killed in turn under the weight of the collapsing beast. Although this is possible, the Bomarzo soldier is being lifted by the elephant rather than crushed. The biblical elephant would, as Bury (1985) points out, certainly have been an Indian elephant, whereas the Bomarzo is African.
Lang, S., Bomarzo, Architectural Review, no.121, June 1957, pp.427-430
Bury, J.B., Bomarzo Revisted, Journal of Garden History, vol.5, no.2, 1985, pp.213-223