The whole army of Egypt was sent out to bring back the Israelites, with the Pharaoh at their helm, and you term this as Pharaoh letting them go. Then you tell me, I need to read the whole account?
Wow.
The Pharaoh had seen ten plagues leveled on his people. His own son had been struck down during Passover night. Even then he hardened his heart and refused to let the Israelites remain free. This you refer to as him letting them go, as if it was a done deal.
If so, then how is it that he wound up on the bottom of the Red Sea being destroyed with the army of Egypt?
Later...
Interesting story about a large chamber discovered several decades ago that was full of mummies of the time. Later research proves that all the royals but Seti were present. He was missing.
Many analysts argue Seti is the pharoah who drowned which neatly explains his absence.
But yes, read carefully, he lets them go and reneges. Hence he is destroyed by God.
That's another one of those yin-yan things in the Bible. In the end all is complete and there are no loose ends.
BTW, this is a story about a large group that was tributary to the Egyptian ruler. Sure, it's slavery, but it wasn't individual mano y mano slavery ~ think of it more like the Iroquois among the Hurons. They paid in corn and dogs. Then, one day, they ran away to Central New York, climbed to the tops of the highest hills and dared the Huron to come after them.
The Hebrews were paying tribute in bricks.