Lessons from Ai

"In order to understand the problems, first, let's take a look at some of the surrounding facts of the conquest narratives:

• God sends signs and plagues ahead of Israel to drive the pagans out of the land (Exodus 23). 
• The rhetoric in most of the promises pertaining to the conquest seems more concerned with driving the other nations out of the land rather than extermination.
• Rahab clearly responds to the revelation of God through his actions (Josh 2:11). 

True to his nature, God communicates to the pagan nations and gives them plenty of time to turn from their wicked ways. Of course, if you keep reading into the book of Joshua, it becomes evident that the people in the land did not listen to God and experienced his judgment as a result.

There are some tough passages in the Old Testament.
A good example is Joshua 8:16-25 (NRSV):

So all the people who were in the city were called together to pursue them, and as they pursued Joshua they were drawn away from the city. There was not a man left in Ai or Bethel who did not go out after Israel; they left the city open, and pursued Israel.
Then the Lord said to Joshua, “Stretch out the sword that is in your hand toward

Ai; for I will give it into your hand.” And Joshua stretched out the sword that was in his hand toward the city. As soon as he stretched out his hand, the troops in ambush rose quickly out of their place and rushed forward. They entered the city, took it, and at once set the city on fire. So when the men of Ai looked back, the smoke of the city was rising to the sky. They had no power to flee this way or that, for the people who fled to the wilderness turned back against the pursuers. When Joshua and all Israel saw that the ambush had taken the city and that the smoke of the city was rising, then they turned back and struck down the men of Ai. And the others came out from the city against them; so they were surrounded by Israelites, some on one side, and some on the other; and Israel struck them down until no one was left who survived or escaped. But the king of Ai was taken alive and brought to Joshua.
When Israel had finished slaughtering all the inhabitants of Ai in the open wilderness where they pursued them, and when all of them to the very last had fallen by the edge of the sword, all Israel returned to Ai, and attacked it with the edge of the sword. The total of those who fell that day, both men and women, was twelve thousand—all the people of Ai." Wesley Walker

COMMENTARY:
Notice above, as pointed out by Mr. Walker, God sends warnings by plagues (signs) of His power (hence existence) before His final destruction. (as He did in Egypt before the 10th plague of death). Also, Rahab converted based on the judgments sent by God.
So too do these principles apply in the endtimes...