1)
Why will they know "Ki Ani Hashem"?
1.
Malbim: Via the fire that I will out in Egypt, all its helpers will be broken.
2)
What fire will Hashem give?
1.
Rashi: His anger like fire.
2.
Radak citing Targum Yonasan: (This is a Mashal.) I will bring nations strong like fire against Egypt.
3)
Why will Hashem break all its supporters?
1.
Malbim: (a) So no one will help Egypt. (b) So also the land around it will be desolate. This increases the desolation. (c) So "they will know that I am Hashem."
