For 12 years, five kingdoms served Chedorlaomer king of Elam.  In the 13th year, Sodom and the 4 other kingdoms rebelled. In the 14th year, Chedorlaomer made war with them and took all their goods and victuals along with Lot, Abram’s nephew, and all his goods. 

When Abram was informed of Lot’s capture, Abram activated his army of 318 trained servants. Abram had trained them to fight and now he arms them for battle.