According to the historians Livy and Dionysius of Halicarnassus, writing at a far later date, the earliest Roman army existed in the 8th century BC. During this period Rome itself was probably little more than a fortified hilltop settlement and its army a relatively small force, whose activities were limited "mainly raiding and cattle rustling with the occasional skirmish-like battle". Historian Theodor Mommsen referred to it as Rome's "curiate" army, named for its presumed subdivision along the boundaries of Rome's three founding tribes (Latin: "curiae"), the Ramnians, Tities and Luceres. This army's exact structure is not known, but it is probable that it loosely resembled a warrior band or group of bodyguards led by a chieftain or king. Mommsen believes that Roman military organization of this period was regimented by the "Laws of [the apocryphal King Italus" but these laws, though referred to by Aristotle, have been lost.