Three hundred and eighteen men against four armies. That's what Abraham brought to the battle—and he won.
According to Josephus, the trouble started when the cities of Sodom fell under Assyrian control. For twelve years, five Sodomite kings paid tribute to four Assyrian commanders—Amraphel, Arioch, Chedorlaomer, and Tidal. In the thirteenth year, the Sodomites rebelled (Genesis 14:4). The Assyrians responded by laying waste to all of Syria, crushing even the offspring of the giants, before turning their full force on Sodom. The battle took place at the Vale of Siddim, a landscape pocked with slime pits that would later become the Dead Sea. The Sodomites lost badly. Many were killed. The rest—including Abraham's nephew Lot—were taken captive.
When Abraham heard the news, he moved immediately. No council of war, no hesitation. He marched with his 318 servants and three allies and attacked the Assyrian camp at Dan on the fifth night. Some of the Assyrians died in their beds. Others were too drunk to fight. Abraham chased the survivors all the way to Damascus.
Josephus draws a pointed lesson: victory does not depend on numbers. It depends on courage.
On the return, Abraham met Melchizedek, king of Salem—which Josephus identifies as Jerusalem—who was also a priest of God. Melchizedek fed Abraham's army and blessed him. Abraham gave him a tenth of the spoils. When the king of Sodom offered Abraham the remaining plunder, Abraham refused. He would take nothing for himself. Only his allies—Eshkol, Aner, and Mamre—received their share.
Afterward, God appeared to Abraham and promised that his reward for such selflessness would be a son and descendants as numerous as the stars (Genesis 15:5).