British Museum Historian, Kenneth Kitchen, has published images a number of stela from David's time, 1040--970 BCE, which I consider reliable: the Stele of Mat-shc'han places David's birth in Bethelmem of Judea. Other stele place his birth in either Midian or the ruins of S'dom.
David was an ordinary shepherd until the prophet Samuel annointed him in the tents of his father, Jesse.
In the Second Philistine War (circa 1027) the Philistine giant Goliath challenged their King to a champon's battle. Saul was hardly a warrior: he was chosen for his handsome good looks, not his ability as an administrator, soldier, or tactician. David volunteered to fight Goliath.
Saul's armor didn't fit David, so David opted for mobility over protection. Perhaps David was also schooled in guerilla warfare by his father, Jesse. Being a shepherd, David was well experienced with the sling. David slew Goliath. That turned the battle to the favor of Israel.
Virtually constant strife with Palestine has left a number of nasty scars in history.
With a few victories under his belt, David eventuially moved into Jerusalem, and remained there until his death in 970 BCE. His successor was Solomon, son of Bathsheba.