Commentaries:
Notice how different verses 18-19 sound from anything being spoken by the peoples of Israel today. After Jacob's Trouble, Israel will actually grieve and moan due to the correction she receives. She will beg to be brought back to God. Verse 20 shows the unmistakable compassion and feeling that God has for His people, and His determination to lift them out of the pitiful physical and spiritual condition they will be in at that point.
Verse 21 tells of Israel reversing the course of her migration millennia ago, "Set your heart toward the highway, the way in which you went. Turn back. . . ." Israel comes to this condition and pleads for God's restoration before she makes the Second Exodus, just as Israel cried out in Egypt to the God of their fathers, and then God delivered them. If this is correct, the identity of Israel will be recognized sometime during Jacob's Trouble, but before the Second Exodus takes place.
If the patterns of Israel's history remain consistent, God will remind Israel of her obligation to Him, which will include the knowledge of who Israel is. She will not listen—Israel has rarely listened—so God will cause the nations of Jacob to go through such "trouble" as they have never experienced. Though God does not revel in destruction, He knows best what it will take to turn His people around. In the end, the repentant people who remain will be willingly led back to the Promised Land.
David C. Grabbe
The Second Exodus (Part Three)