Here is an interesting theological question!

I'm not sure what to think of this but it raises an interesting question, for me at least.

Now before I present the question let me make sure and acknowledge that God is God and has the right to do whatever He wants.  No problem there.  It's just that what I see here seems to violate some of the characters of God.

Take a look and then I'll explain what I am talking about.

Deuteronomy 2:30-37(NKJV)

“But Sihon king of Heshbon would not let us pass through, for the Lord your God hardened his spirit and made his heart obstinate, that He might deliver him into your hand, as it is this day.

“And the Lord said to me, ‘See, I have begun to give Sihon and his land over to you. Begin to possess it, that you may inherit his land.’ 

Then Sihon and all his people came out against us to fight at Jahaz. 

And the Lord our God delivered him over to us; so we defeated him, his sons, and all his people. 

We took all his cities at that time, and we utterly destroyed the men, women, and little ones of every city; we left none remaining. 

We took only the livestock as plunder for ourselves, with the spoil of the cities which we took. 

From Aroer, which is on the bank of the River Arnon, and from the city that is in the ravine, as far as Gilead, there was not one city too strong for us; the Lord our God delivered all to us. 

Only you did not go near the land of the people of Ammon—anywhere along the River Jabbok, or to the cities of the mountains, or wherever the Lord our God had forbidden us.

Here is how I interpret what I have highlighted.  God forced or compelled this man's heart to harden so that God would have an excuse to turn the man's kingdom over to God's chosen people.  How is that just? 

If the guy had hardened his heart on his own I would have no problem with it, but God forced him to do it.  It's almost as if God caused this guy to sin and then punished Him for it.  If you are compelled to sin, is it really a sin? 

Interesting question in my book.