Here, Isaiah speaks Messianically to two different groups of people. Verse 11 recounts the joy of the saints in the New Jerusalem of America. They will sing a new song (DC 84:98-102), they will rejoice to be in the presence of Jehovah, and they will welcome the returning city of Enoch, 'and we will fall upon their necks, and they shall fall upon our necks, and we will kiss each other' (Moses 7:63). Such will be the joy of the righteous.
Verse 12 emphasizes the identity of the Redeemer at that day. Now the focus shifts to the Jews in Jerusalem, who will be saved in a dramatic fashion at the Second Coming. The Lord says 'I am he,' reminding us of another ominous declaration, 'I am he who was lifted up. I am Jesus that was crucified. I am the Son of God' (DC 45:52). At this point, the Lord reasons with the Jews about their relationship with him. They feared man rather than God (v. 12-13). The Jews had forgotten the Lord and they had 'feared continually every day, because of the fury of the oppressor' (likely referring to the army prophesied to come against Jerusalem just prior to the Second Coming). The Lord asks, 'And where is the fury of the oppressor?' (The fury is gone because the Lord has just destroyed the opposing forces and redeemed Jerusalem). The Lord reminds them that if they had been faithful to him, they would have had no need to worry themselves about the wrath of their enemies, but of course, they did not. Again, in verse 15 he declares his identity to these shocked Jews, saying, 'I am the Lord thy God, whose waves roared; the Lord of Hosts is my name.'
At the end of this dramatic conversation, the Jews will finally realize that they have denied the Christ for two millennia. While they had suffered persecution after persecution from one oppressor and another, it could have all been avoided, if they had trusted in the arm of the Lord. This sad truth will cause them to 'weep because of their iniquities; then shall they lament because they persecuted their king' (DC 45:53).