Exodus 7:5

The ungodly world is hard to teach. Egypt does not know Jehovah and therefore dares to set up its idols and even ventures to ask, "Who is the Lord?" Yet the Lord means to break proud hearts, whether they will or not. When His judgments thunder over their heads, darken their skies, destroy their harvests, and slay their sons, they begin to discern somewhat of Jehovah's power. There will yet be such things done in the earth as shall bring skeptics to their knees. Let us not be dismayed because of their blasphemies, for the Lord can take care of His own name, and He will do so in a very effectual manner.

The salvation of His own people was another potent means of making Egypt know that the God of Israel was Jehovah, the living and true God. No Israelite died by any one of the ten plagues. None of the chosen seed were drowned in the Red Sea. Even so, the salvation of the elect and the sure glorification of all true believers will make the most obstinate of God's enemies acknowledge that Jehovah, He is the God.