One of the questions that needs to be answered from the book of Joshua, and I believe can be answered satisfactorily, is the question that seeks to understand and explain why God ordered the destruction of the seven tribes of Canaan.
This post will not attempt a complete answer, but will give a partial explanation.
One of the reasons this wiping out of the inhabitants of Canaan by the Promised Land bound Israelites is delivered in this quote from Alan Redpath's book on Joshua called Victorious Christian Living:
But I would have you observe that they faced not only conﬂict but victory. God had a purpose for that land. What was it? This-a little babe in a manger at Bethlehem, Christ the Son of God "on a cross at Calvary, one hundred and twenty people in an upper room and the Holy Ghost falling on them. Bethlehem, Calvary, Pentecost: the incamation of the Son of God, the judgment of the sin of humanity heaped on Him, the life of the Son of God incarnate in the the believer; all thin was God's master plan for the salvation of a fallen race. And nothing, I say nothing, on earth or in hell should ever stand in the way of the plan of God. The iniquity of the people was full. Now God begins to act.Certainly, this is not a complete answer, but it is part of the answer.
God was preparing the redemption of mankind in the life, death, and resurrection of His Son. And this was going to take place in Canaan. And though there are many more facets to the explanation, God's plan of redemption is definitely an important one.
Redpath goes on to say, "The purpose of God for every man and woman is Bethlehem, Calvary, Pentecost, and everything that stands in the way of God's fulfillment of His plan must be conquered."