According to 2 Chronicles 28,
Aram-Damascus, under Rezin, and Israel, under Pekah, attempted to depose Ahaz through an invasion. Judah was being defeated and, according to 2 Chronicles 28, lost 120,000 troops in just one day. Many significant officials were killed, including the king's son Maaseiah. Many others were taken away as slaves.
According to Isaiah 7
Isaiah tells King Ahaz that the invasion will be unsuccessful and tells him to ask God for a sign. Ahaz refuses, claiming he does not want to test God. Isaiah then announces that God himself will choose the sign, etc.
Prophet Isaiah's visit to Ahaz in Isaiah 7, was it before or after what happened in 2 Chronicles 28- 5:15?
If the visit and prophecy of Emanuel, was before the horrible things that happened in 2 Chronicles 28- 5:15, then how could the prophecy of Emanuel had been a promise of salvation, protection to the house of David, from the danger of the impending invasion of Aram and Ephraim?