God's Sovereignty Exercised

How is God's sovereignty over nations revealed in His dealings with the kings of Canaan that He caused Israel to war against in the conquest of Canaan? Does God direct all things down to each detail, or does He merely have a plan, with man left to fill in the blanks? Why is the truth of God's absolute sovereignty essential to the Scripture teaching of God and His salvation? How does God show Himself sovereign in creation, providence, salvation, and judgment?