And the men of Judah came, and there they anointed David king over the house of Judah.
2 Samuel 2:4a
David's royal career began with a small endeavor. The tribe of Judah, Just one clan in Israel, acknowledged him as king after Saul's disastrous death in battle. The rest of the nation, once so enamored of David that they praised his exploits in song, were divided and in shock. David has his work cut out for him. He is tasked to "earn" the crown by being a uniter of Israel.
This is not just a political division over ideologies. This divided nation is scattered in a deeply personal way. Even though all of Israel shared one ethnic and religious identity under the worship of Yahweh, the tribalism of the Book of Judges is still a strong undercurrent socially. Most Israelites identify with tribe and family more than with any other affiliation. David must lead in such a way as to overcome this fragmentation, unite the nation, and fulfill God's call upon him. After all, God anointed David to be king over all of Israel while he was still just a shepherd boy. God would use David to unite and strength the nation.
That's David's comfort... God will use David. He will strengthen David's kingdom. It began with just one tribe. It will end in Israel securing new borders, David building Jerusalem into a world class city, and a kingdom being built from the current crisis. God is very adept at turning a crisis into a kingdom. David's life is testament to God's great work. And we can trust that God's power is still as potent today. There is no division that God cannot heal. There is no person that He cannot redeem. There is no trial that He cannot resolve. There is no chaos that God's peace cannot contain.