The Israelites "went up armed out of the land of Egypt", Moses carrying with him the bones of Joseph, as an earlier generation of Israelites had promised Joseph on his deathbed.
"The Lord went before them in a pillar of cloud by day, to guide them along the way, and in a pillar of fire by night, to give them light, that they might travel day and night."
G-d is their spiritual tour guide but their literal one as well, directing the Israelites in a more circuitous route, "... roundabout, by way of the wilderness at the Sea of Reeds" to fit in with His plan.
That would be a final and cataclysmic show of His power before the Egyptians (and the doubting Israelites). He will once again "'stiffen Pharaoh's heart'" so that he and his army will pursue the Israelites who are now easy targets for the Egyptians since they are innocently camped at the banks of the Yam Suf, popularly mistranslated as the Red Sea.
I will let what is arguably one of the most powerfully cinematic moments in the Torah speak for itself:
"As Pharaoh drew near, the Israelites caught sight of the Egyptians advancing upon them. Greatly frightened, the Israelites cried out to the Lord. And they said to Moses, 'Was it for want of graves in Egypt that you brought us to die in the wilderness? What have you done to us, taking us out of Egypt?'
But Moses said to the people, 'Have no fear! Stand by, and witness the deliverance which the Lord will work for you today; for the Egyptians whom you see today you will never see again. The Lord will battle for you; Hold your peace!'
...Then the Lord said to Moses, ...'Tell the Israelites to go forward. And you lift up your rod and hold out your arm over the sea and split it, so that the Israelites may march into the sea on dry ground.'
Then Moses held out his arm over the sea and the Lord drove back the sea with a strong east wind all that night...The waters were split, and the Israelites went into the sea on dry ground, the waters forming a wall for them on their right and on their left. The Egyptians came in pursuit after them into the sea, all of Pharaoh's horses, chariots, and horsemen...(G-d) threw the Egyptian army into a panic. He locked the wheels of their chariots so that they moved forward with difficulty...
Then the Lord said to Moses, 'Hold out your arm over the sea, that the water may come back upon the Egyptians...The waters turned back and covered the chariots and the horsemen...not one of them remained. But the Israelites had marched through the sea..."
And how do the Israelites mark this miraculous moment? Perfectly appropriate for this Grammy Awards' weekend, they croon the Shira ha-Yam, the Song at the Sea:
"Then Moses and the Israelites sang this song to the Lord. They said,
'I will sing to the Lord, for He has triumphed gloriously;
Horse and driver He has hurled into the sea.
The Lord is my strength and might;
He is become my deliverance.
This is my G-d and I will enshrine Him;
The G-d of my father, and I will exalt Him...
In Your love You lead the people You redeemed;
In Your strength You guide them to Your holy abode...
The peoples hear, they tremble...
The Lord will reign for ever and ever!'
Then Miriam the prophetess, Aaron's sister, took a timbrel in her hand, and all the women went out after her in dance with timbrels. And Miriam chanted for them:
'Sing to the Lord, for He has triumphed gloriously;
Horse and driver He has hurled into the sea.'"