This post is adapted from Luther's Works, vol. 18 (Lectures on the Minor Prophets I).
When the destruction of the Jewish people was imminent, when the new age and kingdom—namely, Christ—were coming, God sent many great prophets to cry out and lament about the coming destruction of the entire people so that at least some who heard the preaching of a threatening evil might believe, be converted, and, thus converted, be saved. In this way they might delay that terrible and wretched destruction. Thus at the same time prophesied Amos, whom I regard as the first, Hosea, who must be counted after Amos, and Micah. Isaiah also prophesied at the same time, although he would have been the last of these. Now all of them prophesied about the destruction of the old people and the bringing in of a new people, about the abolition of the external kingdom and the establishment of a new spiritual kingdom which would happen through Christ.