The Israelites have finally made it out of Egypt, through the wilderness, and across the Jordan. Through much complaining, trial, blessing, judgement, and miracles, Israel had finally made it to the promised land. As you examine their conquest (read Joshua chapters 5-12 for the full story), there are several lessons to be taken.
First of all, you see that this generation had the faith in God which their fathers lacked. God had promised them the land. He promised that all of the nations dwelling their would be subdued. In Leviticus 26, he says:
"If ye walk in my statutes, and keep my commandments, and do them... And ye shall chase your enemies, and they shall fall before you by the sword. And five of you shall chase an hundred, and an hundred of you shall put ten thousand to flight: and your enemies shall fall before you by the sword." -Leviticus 26:3,7-8
Despite all the promises God made, when the spies went in to search, they were still afraid and did not have faith that the Lord would give the land to them. All they had to do was trust God, and He would give them the victory, but they were too afraid to grab ahold of the blessings God had for them, so God punished them and would not allow them in the land. Fast forward 40 years later and Israel is faced with the same decision. This time, they go out in faith and God rewards them for that faith with victory and control over the land.
If you read the chapters, you'll notice in every victory (not including their defeat at Ai), there is no recording of struggle, close victories, or heavy losses. In each battle, Israel utterly destroys their enemy with little or no report of any Israelite casualties. Once again, all they had to do was trust God to give them the victory in order to take ahold of His promise. Look at chapter 12 verse 24 and you will see that under Joshua, Israel overcame and killed 31 kings of other nations. It is unheard of for any one nation to overthrow 31. Not only that, but Israel had the disadvantage of having been wandering for years before and some of those they went up against had walled cities in which to defend themselves. Such victory would be impossible by chance. Only God could give them so many victories. He gave them the promise that He would do it, and all they had to was take ahold of His promise.
Now look at Israel's only loss- the first battle at Ai. Comparitively, it seems like Ai was one of the least intimidating of their foes, as evidenced by chapter 7 verse 3:
"And they returned to Joshua, and said unto him, Let not all the people go up; but let about two or three thousand men go up and smite Ai; and make not all the people to labour thither; for they are but few."
This was supposed to be one of the few "easy victories" for Israel. One would think that even without God's intervention, Israel could still win this one. However, because of Achan's sin (see Joshua 6:18-19 and 7:1), the Lord was not on their side. As a result, Israel was defeated and humiliated. This shows us that God was not just the one who gave Israel victories which they couldn't have won alone. God was their victory, and the absence of God's help was their defeat. Every single battle was dependant on God. Don't we do the same thing sometimes? Don't we trust God with the big things in our life, but we try to do what is "manageable" on our own?
The battle in chapter 10, on the other hand, would seem like one of the toughest opponents Israel had to face. Five kings had aligned against Israel out of fear that Israel would continue to win battles and destroy them one by one. Once again, when it comes to the battle, it doesn't even sound like Israel even struggled, but what is even more interesting is that in chapter 10 verse 11, it says:
"And it came to pass, as they fled from before Israel, and were in the going down to Bethhoron, that the LORD cast down great stones from heaven upon them unto Azekah, and they died: they were more which died with hailstones than they whom the children of Israel slew with the sword."
God made sure that Israel knew that it was He who won their battles. He didn't want them to be prideful. He made sure they knew that He had given them all of these battles, all they had to do was go out in faith and obedience and grab ahold of the blessings.
The verse that sums up this section is in chapter 10 at the end of verse 14:
"And there was no day like that before it or after it, that the LORD hearkened unto the voice of a man: for the LORD fought for Israel."
Notice, it doesn't say He fought with Israel, but for Israel. You see, when we do what the Lord says, He will come through with His promises. All we have to do is go out in faith and obedience and grab ahold of the Lord's promises, and He will give us the victory.