While not the only theme of the book of Joshua, a strong current within the text is a handbook, if you will, regarding the qualities necessary in righteous leadership. Joshua is not the first significant leader of the Old Testament; he follows Abraham, Noah, Jacob, Moses, and Aaron. However, his lot is given to him from the former leadership of Moses — the one who lead the people of God out from the hands of Pharoah. He came to leadership having apprenticed under Moses and learned the habits of leadership, and consequences of failure, vicariously through Moses.
God establishes a relationship with Joshua that is grounded in Joshua having a personal experience witnessing God’s hand on His follower Moses: “Only be strong and very courageous, being careful to act in accordance with all the law that my servant Moses commanded you; do not turn from it to the right hand or to the left, so that you may be successful where you go” (Joshua 1:7). God restates this encouraging message a few verses later. Joshua, in turn, speaks to his leadership regarding what God expected of them as a nation. It is through their response to Joshua that we can see his effectiveness as a leader: “Whoever rebels against your orders and disobeys your words, whatever you command, shall be put to death” (1:18). They echo the words of God and encourage their leader in the final verse of chapter 1, “Only be strong and courageous.” Joshua commands and the people act. And God responds by exalting Joshua (4:14).
Joshua’s actions also prove a leader of an immediate nature. We see time and time again Joshua rising early and going out to act upon the commands of God. When he learns of Achan’s betrayal, he responds immediately and without hesitation. He commands that his leadership get the five kings from the cave, and they do so. His judgment upon them is swift and decisive.
Another aspect of the book of Joshua that is valuable to the building of the foundation in the Old Testament is in chapter 24. Verses 1-13 retell the story of God’s chosen people from Abraham to Jacob to Moses and the exodus from Egypt to the 40-year wandering to the time of Joshua and the people conquering the lands. Joshua uses this history of his people to reinforce the goodness of God, His mercy to the people, and, additionally, the judgment of God when His people turn away in sin. The people respond correctly in that they will not turn away: “Far be it from us that we should forsake the Lord to serve other gods…” (24:16). It is as if Joshua needs a commitment from God’s people whom he has been entrusted to lead that they will continue to uphold the covenant and honor God as a jealous and merciful God.
Joshua is a warrior of God who leads from the front trusting in the promise of the Lord of his ancestors. Therefore, this book is not so much about the people thriving and failing under God as it is a testament to a wise, strong, and decisive leader.