You will not have to fight this battle

In 2 Chronicles 20 and army comes against Jehoshaphat and he prays a great prayer that ends with

For we have no power to face this vast army that is attacking us. We do not know what to do, but our eyes are upon you.2 Chronicles 20:12

I seems to be back with the desperation again.
God answers by a prophecy through Jahaziel that ends with

17 You will not have to fight this battle. Take up your positions; stand firm and see the deliverance the LORD will give you, O Judah and Jerusalem. Do not be afraid; do not be discouraged. Go out to face them tomorrow, and the LORD will be with you.'

A lot of times Israel did have to fight the battle, but for this one, they didn't. The enemies killed each other before Israel got there and so God had delivered them. Sometimes we have to fight for deliverance and sometimes it's all God's work.