In spite of the devastation, there will be a redemption. There are two types of people who will be redeemed at that day. One is a branch of Israel who have escaped. Isaiah does not declare who those people are, but certainly there were some who were able to flee before the destruction. Of course, in the Nephite reading of this chapter, the branch would point to the Nephites, even though they came much later in time.
The second group who will receive redemption are the righteous who remained in Israel. Jehovah had already said that all would be well with the righteous, and now indicates that Jehovah will watch over the righteous who remained in the city.