The traditional account of Roman history, which has come down to us through Livy, Plutarch, Dionysius of Halicarnassus, and others, is that in Rome's first centuries it was ruled by a succession of seven kings. The traditional chronology, as codified by Varro, allots 243 years for their reigns, an average of almost 35 years, which, since the work of Barthold Georg Niebuhr, has been generally discounted by modern scholarship. The Gauls destroyed much of Rome's historical records when they sacked the city after the Battle of the Allia in 390 BC (Varronian, according to Polybius the battle occurred in 387/6) and what was left was eventually lost to time or theft. With no contemporary records of the kingdom existing, all accounts of the kings must be carefully questioned.