These verses explain that in the second year of Saul’s reign he gathered together an army to fight against the army of the Philistines. It is very interesting to note that Jonathan (verse 2) was in charge of a thousand men. I would suppose Jonathan was at least 20 years old, perhaps older. This would make Jonathan approximately 28 years older than David. In almost all the children’s stories I have read, Jonathan and David are pictured as being about the same age, but they are not.

My calculations:

I Chronicles 29:27 and I Kings 2:11 - David ruled 40 years.

II Samuel 5:4,5 – David was 30 years old when he began to reign and, "in Hebron he reigned over Judah seven years and six month: and in Jerusalem he reigned thirty and three years over all Israel and Judah."

II Samuel 5:4 - David began his reign over Judah when Saul died. David was 30 years old at the time.

Acts 13:21 - Saul ruled 40 years.

Therefore, Saul had been ruling 10 years when David was born.

I Samuel 13:1 states, "Saul reigned one year; and when he had reigned two years over Israel," Therefore: when Saul had ruled two years, it was eight years until the birth of David.

The difficulty with understanding that Jonathan is about 28 years older than David is that Saul must be approximately 20 years older than Jonathan. If we estimate that Jonathan is 20 in the second year of Saul’s reign and that Saul is 20 years older than Jonathan and that Saul will rule another 38 years before his death, this would make Saul 78 years old at his death.

Frankly, it doesn’t seem right to conclude that the Israelites would allow their king, who is 78 years old (and likely older), to go to battle. It might be that Saul didn’t fight, but simply controlled the battle from a safe vantage point, until the enemy overran the Israelite forces and destroyed his headquarters.

Another point is the age of Jonathan at his death. If Jonathan was about 20 years old in I Samuel 13:1,2, he would be approximately 58 years old in I Samuel 31. I suppose Jonathan would also be a leader, instead of a fighter, and would command the battle from a safer vantage point than the heat of battle, which explains why he was with his dad in death.

Later, when David was king, the Israelites refused to allow him to go to battle as he approached old age. Perhaps the Israelites learned a valuable lesson when Saul was killed, that they didn’t want to repeat with David.

Another point that enters into this discussion is Mephibosheth. II Samuel 4:4 states that Mephibosheth was five years old when Jonathan was killed in battle. If Jonathan was 20 years old in I Samuel 13:1,2, then he will be approximately 53 years old when Mephibosheth was born. If, as stated on On-Line Bible, Jonathan was approximately 30 years old, he would be 63 years old when Mephibosheth was born. This, of course, also makes Saul older, likely about 85 years (at the youngest) when he was killed.)