David's Empire
David, Israel’s second king and God’s appointed king, ruled first over Judah only and made his capital at Hebron. After a little over 7 years the other tribes asked him to rule over them as well. It was at this time that he united the tribes and made Jerusalem his new capital. He gave them a well-organized central government and law, a national consciousness, and an individual identity.
The kingdom of Israel was established and in the control of David and his mighty army. If there was any sort of problems on foreign soil David's army was in a position to wage war. There were many such wars and God was with him and king David built what may accurately be referred to as an "empire."
David's kingdom was not necessarily a military government as it was with king Saul, although David made many more conquests than king Saul. Although David was a man of war the strength of his rule did not depend on military victories. Besides being a military leader David was also a statesman and his government was well organized and staffed. His army under Joab or himself was rarely if ever defeated.
The result was that his borders were continually enlarged until an empire was formed.