Moses' demand that Pharaoh 'let the people go' is commonly understood as a plea for freedom from slavery.  However, as we take a closer look at the Exodus story it becomes quite clear that Moses was making a request for 'freedom of religion' rather than freedom from slavery.

YHVH instructed Moses at the burning bush to:

"Go to the King of Egypt and tell him: YHVH, the Elohim of the Hebrews had come and told us, we must embark upon a journey of a three day distance into the desert to offer sacrifices to our Elohim."  (Ex 3:18)

This request made no mention of freedom from slavery.  Instead, Moses was instructed to demand that Pharaoh allow Israel the right to worship their Elohim in the desert, at a site three-day distance from Egypt.

"Moses and Aaron came to Pharaoh and said: Thus says YHVH, the Elohim of Israel, let My People go and worship Me in the desert."

When Pharaoh refused they answered: "The Elohim of the Hebrews has called upon us to embark upon a journey of a three day distance into the desert in order that we may sacrifice to YHVH our Elohim, lest He strike us with pestilence or sword."  (Ex 5:1-3)

Again, all that Moses requested was that Israel be allowed to worship YHVH in the desert.  The final phrase: "lest He strike us with pestilence or sword" was a warning to Pharaoh that should he not allow them this journey to worship YHVH, a severe Divine punishment will ensue and many people, Egyptians and Hebrews, will die.  Moses' demand implied that it was in the best interests of the Egyptian people to allow Israel this short 'spiritual retreat' in the desert.

The result of this first encounter was disastrous, as Pharaoh not only said no, but also doubled Israel's workload.  (Ex 5:4-10) Nonetheless, YHVH commanded Moses once again to go to Pharaoh and demand that he grants them permission to worship Him in the desert.  This time, however, YHVH provided Moses with some 'leverage' by performing miracles for the purpose of convincing Pharaoh to take his warning seriously.  Pharaoh's refusal: "I never heard of this YHVH" (Ex 5:2) led to the plagues, in effort to convince him that YHVH, the Elohim of the Hebrews, exists and will bring plagues if His people do not worship him:

"Pharaoh will not listen to you, so I will put My Hand against Egypt with great punishments, so that Egypt will know that I am YHVH."  
(Ex 7:4-5)

It took Ten Plagues to finally convince Pharaoh that the pestilence and sword they suffered was because he would not allow Israel to worship their Elohim.  After the tenth plague Pharaoh finally allowed them to leave, but only in order to worship YHVH.  He never granted them freedom from slavery or permission to leave Egypt.

"Go meet Pharaoh in the morning and say to him: YHVH, the Elohim of the Hebrews sent me to you demanding, Let My People Go and worship Me in the desert, and behold you have yet to listen.  Thus says YHVH, with this plague you will know that I am YHVH."  (Ex 7:14-17)

In each plague we find an almost identical opening warning: "Let My people go so that they can worship Me in the desert or else." Religious freedom to worship was all that Moses ever requested. Never once did he ever hint to Pharaoh that Israel planned to leave for good!

As we follow the various negotiations that took place between Moses and Pharaoh during the Ten Plagues, we find that they focused only on the 'three day journey' to worship YHVH.

After the fourth plague, Pharaoh granted Israel permission to worship, but not in the desert.  (Ex 8:21-23)  Moses rejected it saying that if Israel offered sacrifices in the land of Egypt, they would be stoned.  Therefore he insisted that they could only worship YHVH in the desert.  Pharaoh agreed to a short journey into the desert, but not a three-day distance:

"And Pharaoh said, I will send you out so that you can worship YHVH your Elohim in the desert, but don't go too far away." But once that plague ended, he hardened his heart again and reneged on his promise.  (Ex 8:24-28)

After Moses warned of the impending plague of locusts, Pharaoh's own servants demanded his concession to Moses.  In response, Pharaoh entered into a new round of negotiations with Moses, which eventually reached an impasse over the issue of who could leave.  Moses insisted that even the women and children would be allowed to come along, while Pharaoh allowed only the men to leave.  (Ex 10:7-11)  The reason Moses insisted on allowing the women and children to join was "for all family members need to worship YHVH".  Never did he tell Pharaoh that everyone must go because the entire nation planned to leave for Canaan.

After the ninth plague Pharaoh conducted one final round of negotiations, this time granting permission even for the women and children to leave, but not their sheep and cattle.  Again Moses insisted that they had to take all the animals, since they did not know what YHVH would require for the sacrifice.  (Ex 10:24-26)

At every stage of the negotiations Moses consistently rejected any concession or compromise, insisting that everyone had to go.  Still, he never suggested that they planned to leave for good. Pharaoh, no matter how resolutely he stuck to his hard line, never suspected that Israel might be leaving permanently.

After the Tenth Plague "Pharaoh called Moses and Aaron at night and said: Get up and get out, and go worship YHVH as you originally requested.  Even your sheep and cattle take with you, as you requested, and bless me as well."  (Ex 12:29-36)

The tenth plague brought Pharaoh to the realization that Moses' original warning of 'pestilence or sword' had actually come true.  Finally he gave in to the very last of Moses' demands, permitting the sheep and cattle to go with them.

Not only did Pharaoh allow Israel a three-day journey to worship YHVH, he also requested that they pray on his behalf.  Even after the Tenth Plague Pharaoh only permitted them to worship YHVH in the desert.  That was all that Moses ever asked for. The entire Egyptian nation also urged Israel to leave as quickly as possible, hoping that would bring an end to the plagues.  When Pharaoh found out that his slaves ran away he was totally astonished:

"It was told to the King of Egypt that the people had run away."  (Ex 14:5)

He was shocked because he realized that Israel did not continue to travel into the desert as planned.  At first they went toward the desert but in the middle of that journey YHVH suddenly commanded them to turn-around.

"YHVH told Moses, tell Israel to turn around and set up camp near the Red Sea, in order that Pharaoh will say they are wandering in the land of Egypt, for the desert has closed them in."  (Ex 14:1-4)

YHVH commanded them to turn around in order to convince Pharaoh that they were not going to the desert.  Had they continued on their journey towards the desert, Pharaoh would have had no reason to chase them.  It was because they did not go into the desert, but instead turned around to go back to Egypt and set up camp by the Red Sea, that Pharaoh concluded: "What have we done, for we have set Israel free from their slave labor."  (Ex 14:5)

Only at that point Pharaoh realized that Israel left slavery.  What led him to this conclusion?  It was the fact that Israel did not travel to the desert as they had requested, they did not return to their homes in Goshen (to their slavery), nor did they travel towards Canaan.  Instead, they stayed in Egypt, and set up camp by the sea.  Pharaoh reached the obvious conclusion: that they declared their independence in the Land of Egypt. Therefore, for the sake of national security, he immediately declared war on them.  (Ex 14:6-10)  If he don't attack first, surely they will attack him, he reasoned.  They were numerous, and armed.  (Ex 13:18)  This was Egypt's greatest fear from the very beginning.  Israel had become so numerous that the Egyptians feared that they would take over their own country.  (Ex 1:8-10)  Thus, Pharaoh's decision to attack ultimately led to Israel's salvation at the Red Sea.

This is the real story of the Exodus.  Despite the popular understanding that 'Let My People Go' was a request for freedom from slavery, the Torah says that it was a request to worship YHVH in the desert.