Exodus 8:1 - 4

"Then the Lord said to Moses, 'Go to Pharaoh and say to him, "This is what the Lord says: Let my people go, so that they may worship me. If you refuse to let them go, I will send a plague of frogs upon your whole country. The Nile will teem with frogs. They will come up into your palace and your bedroom and onto your bed, into the houses of your officials and on your people, and into your ovens and kneading troughs. The frogs will come up on you and your people and all your officials."'" NIV translation

The Egyptians had a god named Hapi who they credited with providing nourishment to the people and it was depicted with a frog in its mouth. The battle of the gods continues with the Lord declaring that He would turn their so called blessing into a curse. 

Exodus 8:5 - 7

"Then the Lord said to Moses, 'Tell Aaron, "Stretch out your hand with your staff over the streams and canals and ponds, and make frogs come up on the land of Egypt."' So Aaron stretched out his hand over the waters of Egypt, and the frogs came up and covered the land. But the magicians did the same things by their secret arts; they also made frogs come up on the land of Egypt." NIV translation

Once again, the stubbornness of Pharaoh was demonstrated as he refused to comply with God's demands. Aaron called up frogs but the magicians did the same thing.

Exodus 8:8 - 11

"Pharaoh summoned Moses and Aaron and said, 'Pray to the Lord to take the frogs away from me and my people, and I will let your people go to offer sacrifices to the Lord.' Moses said to Pharaoh, 'I leave to you the honor of setting the time for me to pray for you and your officials, and your people that you and your houses may be rid of the frogs, except for those that remain in the Nile.' 'Tomorrow,' Pharaoh said. Moses replied, 'It will be as you say, so that you may know there is no one like the Lord our God. The frogs will leave you and your houses, your officials and your people; they will remain only in the Nile.'" NIV translation

Pharaoh appears to have given in to the will of God as he asks Moses and Aaron to pray to the Lord on his behalf. It appears that he has offered unconditional surrender but, as we shall see, that is not the case.