Hashem brought ten plagues upon Pharaoh and his people. He knew that of the plagues, from the first to last of them, it would be the last plague, the plague of the first-born, that would have Pharaoh immediately letting the Jews leave his country. Yet because Hashem wanted to punish the Egyptian people with much punishment and show the people of the world his power and his might, he did not bring the plague of the first-born to begin with, but started out with lighter plagues and from time to time pressed them so that they suffered more and more until they submitted fully and sent the Jews out of their land.
The ten plagues that came upon the Egyptians were like a serious war that is waged between a powerful king and his people who have disobeyed him. This is comparable to a flesh-and-blood king who has an uprising leveled against him. First, he sends his army to surround the state and stop up the water wells. After that he frightens the rebels with shofar (horn) blasts and the shooting of arrows at them. If they don’t give up, the king comes at the head of a great and powerful army and kills their animals, pours scalding matter on them, throws heavy stones at them, fights with them with a powerful army, detains and jails them until he orders the capture of the main rebels and kills them.
The moral of this is: Hashem Yisboroch (Gd), the great king, set out to humble the Egyptians, the people who did not listen to his orders. In the beginning Gd transformed the waters in Egypt to blood. In the plague of the frogs, he made them hear powerful and frightening voices. The plague of lice was like stabbing arrows. The plague of wild animals and the plague of pestilence killed off the animals of Egypt. The plague of boils burned them like kerosene. The plague of locusts was like soldiers who obliterated the fields and gardens. The plague of darkness was like captives being locked up in jail. And finally the plague of the first-born, which had the most significant impact of all. Pharaoh, who was a first-born, was afraid that he would be killed and therefore quickly sought out Moshe and Aharon and begged them to leave his land along with all the Jews.
