But God made the people take a round-about way, the way of the wilderness of the Red SeaThis reversal of B'nei Yisrael (or rather their route) is rather odd. Why not take them directly to Yam Suf? Why do they have to wait there? Why send them on one path only to tell them to turn around and go another way? Shouldn't God have just said "Go to Yam Suf"? Yitziat Mizrayim is the seminal event in Jewish history but wouldn't the Exodus have been "good enough" with the Jews leaving, why did God have to drown Pharoah? If as the Rambam suggests that God cannot change his mind what is going on here? Clearly God must have done this on purpose.
The Ben Ish Chai - R' Yosef Chaim Baghdadi - says that Pharaoh is a man who uses trickery and deception and God does this to turn the tables on him. God couldn't just let B'nei Yisrael go without doing something to punish Pharaoh and his soldiers. The reversal of B'nei Yisrael's route was all part of God's plan to convince Pharaoh to send his army out after them - think smoke and daggers.
Maybe I had the Super Bowl on my brain - sorry ADDeRabbi, I'm not having a Super Bowl party this year, the Steelers and Eagles aren't playing - but it seems to me that this sounds like a football play. Fake right draw them into the back field and we'll head left and they'll never know what hit 'em.