Land is the key theme of Joshua. The book opens with God commanding Joshua to lead the people across the Jordan in the land that he is going to give them. The body of the book focuses on the conquest and allocation of the land.
The roots of this theme reach back to the dominion blessing of Genesis 1:26-28. The ability to carry out dominion over the earth as intended by God was lost apart from redemption.
The promise of land was given to the Israelites as a part of God’s redemptive plan. Like the original dominion blessing, the promised land was given by God, but the recipients were to act on the gift to bring it to fruition.
Joshua shows the dominion blessing in the context of the Fall. The land must be conquered from human enemies who have corrupted the land with their sin. The sinners are to be exterminated from the land, and God’s people are to live in the land in accordance to God’s covenant regulations. In this way the nations will be able to see what a land under righteous dominion looks like.