11 In that day there will be a great mourning in Jerusalem, like the mourning of Hadadrimmon in the valley of Megiddon.
they will be great mourning – of repentance, when the Jews realize that they crucified their God. This will be the final repentance of Israel before Christ returns, when all Israel is saved (Rom 11:26). In that Day, “whoever calls on the name of the Lord will be saved, for in Mount Zion and in Jerusalem there shall be deliverance” (Joel 2:32; Rom 10:13).
like the mourning in Megiddo – which is Armageddon in Greek. Here, is the likely meaning of Armageddon in Rev 16:16. The nations are gathered together when the inhabitants of Jerusalem repent, then the end will come.
This is a comparison to the mourning for King Josiah, who was slain by the King of Egypt in Megiddo , in 609 BC, as recorded in 2 Kgs 23:29–30, and 2 Chr 35:20–25. For Josiah, the prophet Jeremiah “wrote a dirge,” 2 Chr 35:25; and all the minstrels of his country “spake of him in their dirges” 2 Chr 35:25.