[CWOJackson]

He defeated a mighty army...not bad for a shepherd.

[Zechariah11]

But let's not think of him as a snotty-nosed kid with a slingshot, but as a young man who could use a sling deftly (eg. lion, bear). He had a huge faith and was backed by the army of Saul (eg. Jonathan, his brothers, et.al) who did the mop up work while David beheaded Goliath. (No AP reporters around to cry foul on that!)

If you want to really look at his generalship, you'd have to look to later when he was a regimental commander in Saul's army (remember his FedEx delivery of 200 Philistine foreskins to Saul for Michal? The Palestinians are still upset about that.).or when he was the general in command of his own forces at the Cave of Adullum, but far more likely the conquest of many surrounding countries as King.

Btw, his dalliance with Bathsheba occurred when he was at the palace instead of in the field with his army. @ Samuel 11:1 suggests he should have been with his army.

My understanding is that when military strategy of the Bible is studied (and has been by the modern Israeli army), it is the Book of Judges that is looked at.