Second Nephi 19:3 and the Revised Standard Version of the Bible (following many ancient manuscripts) delete “not” in the second line of Isaiah 9:3. The Light brings an increase of joy to the people of Israel.
Reasons are given in verses 4–5 for the increase of joy spoken of. The yoke and staff and rod have been broken; the oppressors—enemy armies and sin—have been taken away.
The Book of Mormon deletes “as in the day of Midian” at the end of Isaiah 9:4. Perhaps Nephi saw little relevance in that phrase for his own people or for us in the future.
The battles that the hosts of Israel, God’s people, are fighting, especially in these last days, certainly are “with confused noise.”