What about God hardening Pharaoh's heart and sending His people to war?
I've been reading the Old Testament lately and I'm having a hard time understanding when God gardens people's hearts. It happens with Pharaoh and it happens in Joshua (currently reading): "For it was the LORD's doing to harden their hearts" Joshua 11:20a. Like I just don't really understand what is happening when it says God hardened their hearts. One argument a professor brought up was that since God hardened pharaoh's heart was it pharaoh's fault that all the plagues occurred? Or since it was God, how can we blame pharaoh, and how can God be justified in the plagues (exodus) and the destruction of many kingdoms (Joshua).
I think it's a little bit of both. God hardens his heart and Pharaoh hardens his own heart. Your question is asking did one cause the other and the answer is God is timeless. Does God harden the hearts of those whose hearts are already hardened? Or does He see in what we call the future, the fact that some people will never accept Him and therefore use that for His glory regardless. For a timeless God those are the same thing.
We also often read into the phrase "hardened heart" as meaning "he can't be saved", but if we look at the Bible that's not how God works. Ezekiel 36:26 "And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh". Jeremiah 24:7 "I will give them a heart to know that I am the Lord, and they shall be my people and I will be their God, for they shall return to me with their whole heart." So while God may harden a heart for a time it doesn't mean that His ultimate saving Grace has become null and void. Take Judas for example. He choose to reject Jesus, but does that mean that Judas could not have been saved? Judas kills himself, while the thief on the cross was saved in the dying moments of his life. Pharaoh was hardened into pursuing Moses and into his own death, but was God's grace ultimately not still available to him in the final moments of his life?
The thing that is scary and yet real though is that in the timeless nature of God, He knows when there are people who will not accept Him no matter what. In fact, we have to understand that there are people who no matter what we or God does, will never seek the new heart that is in Christ. Thankfully WE don't know who those people are so we preach the good news to all anyways and seek renewal for everyone.
The ultimate irony is when we claim that God hardening the hearts is somehow unfair. Jesus calls this out, because he points out that when God hardens someone's heart, that person is ultimately getting what they want.
When Jesus had said these things, he departed and hid himself from them. 37 Though he had done so many signs before them, they still did not believe in him, 38 so that the word spoken by the prophet Isaiah might be fulfilled:
“Lord, who has believed what he heard from us,
and to whom has the arm of the Lord been revealed?”
39 Therefore they could not believe. For again Isaiah said,
40 “He has blinded their eyes
and hardened their heart,
lest they see with their eyes,
and understand with their heart, and turn,
and I would heal them.”
41 Isaiah said these things because he saw his glory and spoke of him. 42 Nevertheless, many even of the authorities believed in him, but for fear of the Pharisees they did not confess it, so that they would not be put out of the synagogue; 43 for they loved the glory that comes from man more than the glory that comes from God.
So in the case of the conquests, we also have to check what our arguments are. It's so unfair that God ordered them to be killed without giving them a chance to repent. What about Rahab? Or what about Ruth? Even in the Levitical laws there are provisions for people who want to join the Israelites. They were given the chance, but they ultimately proved that they did not want it and would never want it and would even fight against it. Another good example of that is Saul. David refused to kill him though he had the opportunity twice. It wasn't because killing was wrong (David killed a lot), but because he felt so strongly that it was not God's will to kill him and that ultimately God would kill Saul via his own means.
Because take that argument (it's unfair for a loving God to send His people to war) and apply it in other circumstances. When FDR sent American troops to fight in WWII, did he do it because he hated all Germans and Japanese and Italians? Do we say that FDR was unloving to the world? Do we blame the soldiers for killing those people instead of just saying "hey guys, come on, stop fighting". No because we understand that love and righteousness and justice and mercy can all exist in the same place, even in the midst of war.