All ancient books of history, Biblical or secular, are written for their object lessons. Ancient historians were not interested in just telling the stories of what happened, nor of charting social movements across time, but they told the stories of great men, great battles, great villains to highlight the lessons to be learned. Maybe it is because I just led a study of the book of Judges, but I think it may be one of the most obvious collections of object lessons out of any ancient history.
Most are aware of the cycle of the Judges: Israel sins. God punishes Israel. Israel repents and cries out to God. God sends them a Judge to save them from their oppressors. There is peace in the land during the life of the judge, but after he dies, Israel again sins and the cycle starts over. Many studies of the book of Judges start and end with that cycle, but there is so much more to the book that that. First, it isn't so much a cycle as a spiral, as Israel's sins get worse and worse and God's punishments get more and more severe. (Compare Jdgs 3:7 with 10:6 and then 3:8 with 10:7) Surely there are lessons we can learn from that. More interesting to me is the fact that every excuse given for the failure of the Israelites to complete the conquest of the land is answered by the various salvations performed by the judges.
In Judges 1:19 the tribe of Judah could not drive out the inhabitants of the valleys because they had chariots of iron. From this point, the rest of the chapter is a litany of failure as tribe after tribe did not drive out the inhabitants of the land as God had commanded. Often the reason given is that the Israelites wanted to keep them around as slaves, but by the time of Deborah the Israelites were enslaved to these same Canaanites. Vs. 34 says the Amorites forced the tribe of Dan up into the hills and would not allow them into the coastal areas. In all of these cases we see the Israelites making decisions based upon their own strength, their own wisdom, and their own desires rather than following God's instructions in faith. Reading between the lines, their concerns seemed to be the numerical superiority of the Canaanites, the superiority of the Canaanites' weapons, and their own desires for slaves and, maybe, just friendly neighbors.
By the time of Deborah the questions of fighting against a numerically superior foe who has better weapons should have been answered by Othniel's victory over an empire-building king from Mesopotamia. The idea of friendly neighbors should have been answered by the Moabite oppression, relieved by Ehud in a secret agent mission worthy of 007, and by the early troubles with the Philistines, answered by Shamgar. Now, the erstwhile Canaanite slaves have banded into a coalition headed by Jabin, king of Hazor and they have enslaved the Israelites. Sisera, commander of Jabin's army, had 900 chariots of iron at his disposal. These chariots were rather long wagons with high sidewalls which protected the multiple archers who rode in them. They were as nearly impregnable in their day as M1A1 Abrams main battle tanks are today against foot soldiers. When God commanded Deborah to send Barak to fight against Sisera, Barak had only 10,000 infantry men. Human wisdom said that Barak did not have a chance. His army would be run down, trampled upon, and shot to pieces. However, God fought on Israel's side and they won a decisive victory. If you trust God, maybe you can defeat chariots of iron.
Gideon then takes on an enemy as numerous "as the sands on the seashore" (7:12), a phrase normally reserved for Israel and the fulfillment of God's promise to Abraham. Gideon had all of 300 men with him. Though the Israelite army later joined Gideon for the mop-up and pursuit, the greatest slaughter of Midianites occurred when Gideon only had 300 men with him. If God is on your side, maybe the enemy's numbers don't matter?
Gideon and Jepthah both conquered cities. Samson vividly demonstrated that one person plus God is all the army anyone needs. Samson also demonstrated that to "dwell among them" was untenable as his downfall came as a result of being too friendly to his enemies.
Over and over, all the reasons for Israel not driving out the Canaanites, stated or implied, are answered by God every time He saves them via a judge. It is almost as if He is saying, over and over, 'If you had trusted me in the first place, you wouldn't need saving now'.
Just a thought: Maybe the same is true of us today, in our battles against worldliness?
Jude 24-25 "Now unto him that is able to guard you from stumbling, and to set you before the presence of his glory without blemish in exceeding joy, to the only God our Saviour, through Jesus Christ our Lord, be glory, majesty, dominion and power, before all time, and now, and for evermore. Amen."