Chapter 11

Jabin, King of Hazor, recruits the Kings of the north, east, and west to fight together against Israel.  The army he raises is as the sand of the sea.  They come and camp to make war against Israel.  God tells Joshua that He will give them to him, so Joshua attacks first, routes them and sends them fleeing.  They are all killed, and then Joshua hamstrings the horses and burns the chariots, as God had commanded him.  This verse:

15 Just as the LORD had commanded Moses his servant, so Moses commanded Joshua, and so Joshua did. He left nothing undone of all that the LORD had commanded Moses. [Jos 11:15 ESV]

Do not forget that Joshua is not doing these things of his own accord.  We have been told repeatedly why these people were to be so completely wiped out, leaving no descendants, no women who worship other gods, none of that.  These people were entirely evil, sacrificing their own children to gods made with human hands.  Decadent, sinful, beyond repentance.  Israel was executing God's judgement on them, and at the same time claiming the promises God had made as far back as Abraham.  God is using Israel as the instrument of judgement here, just as He will later use Assyria and Babylon to execute justice on Israel for becoming even worse than these that were "devoted to destruction".

Why would these kings continue to fight in view of Joshua's string of victories?

20 For it was the LORD's doing to harden their hearts that they should come against Israel in battle, in order that they should be devoted to destruction and should receive no mercy but be destroyed, just as the LORD commanded Moses. [Jos 11:20 ESV]

In the same way He made the Amorite kings do a foolish thing in attacking Gibeon, so that they would be easy pray for Joshua and the army, He also delivered the rest of these kings, so that they were easily defeated. 

These verses:

21 And Joshua came at that time and cut off the Anakim from the hill country, from Hebron, from Debir, from Anab, and from all the hill country of Judah, and from all the hill country of Israel. Joshua devoted them to destruction with their cities. 22 There was none of the Anakim left in the land of the people of Israel. Only in Gaza, in Gath, and in Ashdod did some remain. [Jos 11:21-22 ESV]

The giants are defeated, with only a few remaining.  Goliath will come from these that weren't killed.  These Anakim were a big part of why 10 of the spies said they shouldn't go in the first time.  They get short shrift here, as if Joshua and the army defeat them easily.  Likely there were so few left that as a race of giants, they were now doomed to die out.  They could not reproduce themselves.

I have heard many say that Israel has never yet inhabited all the land of promise.  What then of this verse:

23 So Joshua took the whole land, according to all that the LORD had spoken to Moses. And Joshua gave it for an inheritance to Israel according to their tribal allotments. And the land had rest from war. [Jos 11:23 ESV]

That looks to me like Israel had all they were supposed to have at that time, else Joshua would still be fighting.  Perhaps the promises to Abraham, and the additional land promised to him that Israel as a nation has never possessed, will be included in the Millennial kingdom?