Hmm, interesting. In another thread, several of us discussed the fight between David and Goliath, and we were quoting various bits of Samuel's first book in which the fight was described. At the time, I argued that David must have been about as big as Saul, because Saul dressed David in his own armor. I didn't consider that maybe Saul's armor was mail, and I certainly didn't know that mail is one-size-fits-all.
No, the fight was not an ambush. Goliath had time to see David approach and size him up ... or down. Goliath was quite contemptuous of this unbearded youth armed with a staff (Goliath didn't mention the sling, I don't know if he didn't notice it or if he totally discounted it). Must have been quite a sight for the Israeli and Philistine soldiers: virtually unarmed youth, against a seasoned warrior who stood "six cubits and a span" -- 9.75 feet or almost three metres
1!
So everybody on both sides saw David sling a stone and saw Goliath fall. Since "the stone sank into his forehead," Goliath was killed (blunt force trauma, bone fragments all through his brain...) but so that the armies were certain Goliath was dead, David took off his head -- with Goliath's own sword! -- and held it up for all to see.
Now as for the veracity of the Bible, that's a whole 'nother discussion and one that probably doesn't belong here. But I will note that archaeologists have repeatedly found terrain and cities where the Bible says they were. I think the historical accounts are also accurate.
1A cubit is traditionally the length from elbow to tip of middle finger, about 18 inches or 457 cm; a span is the distance between outstretched pinky tip and thumb tip, or half a cubit.