Thus says the Lord GOD: Behold, I am against you, O Sidon, and I will manifest my glory in your midst. And they shall know that I am the LORD when I execute judgments in her and manifest my holiness in her; I will send pestilence into her, and blood into her streets; and the slain shall fall in her midst, by the sword that is against her on every side.Notice how, in each statement, God changes how we will know him.
Then they will know that I am YHVH. (1)
And for the house of Israel there shall be no more a brier to prick or a thorn to hurt them among all their neighbors who have treated them with contempt.
Then they will know that I am the Adonai YHVH. (2)
Thus says the Lord GOD: When I gather the house of Israel from the peoples among whom they are scattered, and manifest my holiness in them in the sight of the nations, then they shall dwell in their own land that I gave to my servant Jacob. And they shall dwell securely in it, and they shall build houses and plant vineyards. They shall dwell securely, when I execute judgments upon all their neighbors who have treated them with contempt.
Then they will know that I am YHVH Elohim. (3)
(1) YHVH is the God of relationship. He is Israel's husband, teacher, and protector. When Sidon abuses Israel, they answer to YHVH. Like any good husband when his wife is attacked, YHVH responds with even greater violence.
(2) Adonai means "lord" or "master", and when God says that Israel will know that He is Adonai YHVH, He is indicating that, not only will they know that He is their husband, but also that He is their master. Israel will never be free from persecution or danger by their own power, but only by the power of God. "Never again" ought to be a call to repentance, instead of to arms and activism.
(3) Elohim is the Creator and the Judge of all that He created. He has authority over all nations and lands because he created them. He scattered Israel among the nations and He will call them back again. He never forgot or lost them. He knows exactly where every one of His creations is hiding, and He will rescue or destroy them as He chooses.