Joshua is a book of conquest. For the war-wary it is understandable that we would chafe at God taking land away from inhabitants and giving it to His people – and destroying them in the process. But remember that God was not only blessing Israel, He was judging the nations for their idolatry. I guess you can do that when you are God, right?
Consider the pre-explained context in Deuteronomy 9:4-5:
“Do not say in your heart when the LORD your God has driven them out before you, ‘Because of my righteousness the LORD has brought me in to possess this land,’ but it is because of the wickedness of these nations that the LORD is dispossessing them before you.
“It is not for your righteousness or for the uprightness of your heart that you are going to possess their land, but it is because of the wickedness of these nations that the LORD your God is driving them out before you, in order to confirm the oath which the LORD swore to your fathers, to Abraham, Isaac and Jacob.”
The book of Ephesians is also a book of warfare…spiritual warfare. As you complete Joshua (there is some pretty repetitive stuff in some of these books) you may wish to spend a little time on Ephesians (it is short but packed). And whether we like it or not: “The LORD is a warrior; the LORD is His name.” – Exodus 15:3