According to the Hebrew Bible, Saul was the first king of a united Kingdom of Israel and Judah. His reign, traditionally placed in the late 11th century BCE, would have marked a switch from a tribal society to statehood.
After Samuel tells Saul that God has rejected him as king, David, a son of Jesse, from the tribe of Judah, enters the story: from this point on Saul's story is largely the account of his increasingly troubled relationship with David.