12 then I said, ‘The Philistines will now come down on me at Gilgal, and I have not made supplication to the Lord.’ Therefore I felt compelled, and offered a burnt offering.”
13 And Samuel said to Saul, “You have done foolishly. You have not kept the commandment of the Lord your God, which He commanded you. For now the Lord would have established your kingdom over Israel forever. 14 But now your kingdom shall not continue. (1 Samuel 13:12-14)
In the Old Testament, one could not combine the office of the religious and civic authority. God would not allow the kings of Israel to be priests and the priests to be kings. In 2 Chronicles 26 King Uzziah tried to do the work of priest and God struck him with leprosy. This was the same issue with Saul. He tried to combine the office of the priest and the king.
So it came about, on the day of battle, that there was neither sword nor spear found in the hand of any of the people who were with Saul and Jonathan. But they were found with Saul and Jonathan his son. (1 Samuel 13:22)
As it is the Israelites were outnumbered so badly and to make matters worse, they had no swords. What good is an army without swords?