Thank you for the interpretative question on duration of wars in the Old Testament, “How long were wars in the Old Testament?”
As one reads Joshua, Samuel, and Kings, it appears that wars were only a few days unless it was a siege on a city.
A. The less than a week war:
The armies would line up on opposing side. There may be a champion who will decide the fate of the battle as David and Goliath. The victor would rally the soldiers and the defeated champion would mean disheartened soldiers. The battle was over before it began with the two champions fighting.
When the king or commander was defeated or killed, the soldiers would flee the battlefield. Thus, the battle may last a day or two to determine the outcome. It doesn’t appear to a long drawn-out combat for weeks or months.
The battle between the king of Sodom and the king of Kedorlaomer with their respective allies was a battle that took less than two days (Gen. 14:1–10. The defeated army fled the battlefield and the conquering army would ransack the defeated cities and take whatever possessions or people that they wanted. In Saul’s final battle with the Philistines, the battle was over in a day when Saul was killed (I Sam. 31:1–9). Runners were used to declare the outcome of the battle. The inhabitants of the cities had to decide to flee, surrender, or defend their city.
B. Laying siege to a city.
In the case of a siege of a city, that can take weeks, months or years. It depends if the besieging army can breach the wall, starve out the inhabitants, or negotiate a settlement.
II Kings 6:24–31 says that the siege by Ben-Hadad of Aram on Jerusalem that its people were eating their own newborn babies. There wasn’t any food left in the city. The siege may take months or years until all the food supply ran out and the soldiers were less capable to defend the city wall. King Nebuchadnezzar lay sieged to Jerusalem until it was breached.
Summary: The outcome of two engaging armies usually lasted a day or two, while a siege of a city may last from weeks to years.
-Kingston