Judges 3:2 explains He did this only to teach warfare to the descendants of the Israelites who had not had previous battle experience.  God left people in the promised land for the Israelites to remove by force.

It seems like God would simply send a plague to these inhabitants then Israel could just easily walk into the promised land and occupy it as their new country. Instead, God made Israel strap on a sword, grab a shield and go daily into battle if they were going to realize His promise for them.

Why did God do this?

God wants us to have faith. Without faith it is impossible to please God.

We resist faith. We don’t like the stress having faith requires.

Having faith means not having control or certainty. We don’t like that.

We want everything under control with guaranteed outcomes. But God gets to make the rules so He demands we have faith demonstrated by obedience in spite of our fears and worries.

We have all required faith from our children. Commanding them to jump into our arms at the side of the pool seems simple to us but is always terrifying to young children, yet we do it anyway. We want them to trust us.

God wants us to trust Him. What God asks us to do is simple for God but hard for us because we are unsure of the outcome.

God wants us to learn that He is good and that He loves us very much and that He controls the universe. We can only learn this by jumping into His arms when we hear Him say jump.

Jesus did not jump when He heard satan command He jump in order to test God. We have to learn the difference between God’s voice and the devil’s voice.

The simplest means for distinguishing between the two is God will always call us to obedience while the devil will always call us away from obedience. God will always invite us to trust Him while the devil will cause us to question God’s trustworthiness.

God promises us difficulty in this life but He reminds us that He is with us always. He is at least with those who are busy about His business placing their trust in Him because what they are being asked to do is beyond their own ability to do it.

We need not fear our difficulties we need to face our difficulties looking for God to lead us and strengthen us along the way.