What do Christians take into battle?

Really - ask yourself.

The most obvious instance that called for trust is when the Israelites encountered the Red Sea. However, even from the beginning, we see how they are invited to trust God when he leads them on the longer road, rather than the shorter one through Philistine country to Canaan. They were dressed for battle, but God knew they were not prepared to face down an enemy army at that time; his path was the best path for them.