Adam Clarke on Genesis 14:2

These made war with Bera, etc. - It appears, from Gen 14:4, that these five Canaanitish kings had been subdued by Chedorlaomer, and were obliged to pay him tribute; and that, having been enslaved by him twelve years, wishing to recover their liberty, they revolted in the thirteenth; in consequence of which Chedorlaomer, the following year, summoned to his assistance three of his vassals, invaded Canaan, fought with and discomfited the kings of the Pentapolis or five cities - Sodom, Gomorrah, Zeboiim, Zoar, and Admab, which were situated in the fruitful plain of Siddim, having previously overrun the whole land.