This is the divine title used by the angels in Isaiah’s vision of the glory of God (ch. 6:3). It refers to God as commander of the hosts, or armies, of heaven.
Small remnant.
All of Judea, except Jerusalem, fell into enemy hands. The capital alone stood, seemingly insecure and in desperate peril. Except for this “small remnant” the nation of Judah would have met its doom as certainly as Sodom and Gomorrah.