Moses Parts the Red Sea

Are you familiar with the story of Moses leading the Chosen People out of slavery in Egypt. Maybe you heard it in Sunday school are saw the classic movie "The Ten Commandments." There's a classic moment when the Israelites are being pursued by Pharaoh's army and come up against the Red Sea. At G-d's command, Moses raises his staff and parts the waters, allowing the Israelites to cross safely on dry land. Of course when the Egyptian army ruthlessly follows, the walls of water release and all are killed. Victory!
What I learned today was this: the Egyptian army had decided to leave the Israelites be. G-d had been muddling with them, knocking wheels off their chariots and such, and they decided,"Let's get away from the Israelites! The LORD is fighting for them against Egypt."and retreated. That's right. The Israelites were safe. The army was retreating. And God shot them in the back. I don't know what I find more disturbing, this neglected facet of the story, or that no one else listening to the story seemed disturbed by it.