The first two of the above verses seem to be a general overall description of the year Mormon is describing. It is apparent that the Nephites were left to their own strength, and the power of God had left them collectively. The Lamanites were more numerous and stronger physically than were the Nephites.
Mormon again apologized for what he had to write (v. 8; see also Mormon 4:11–12). He is apparently quoting from Isaiah concerning these things being revealed from the housetops (see 2 Nephi 27:11 where Nephi is quoting the fuller text of Isaiah 29). The knowledge of these scenes of blood and carnage coming to the remnant of these people, and also to the knowledge of the Gentiles (Mormon 5:9), will be through what he is writing and what others have written. It will thus come through the Book of Mormon of our day which is an abridgement of many more records containing a full account of the Nephite and Lamanite people. The “small abridgment” he is writing (v. 9) may refer to his work of abridging the large plates of Nephi, or it could refer to the records of his own day. The former interpretation is the one usually followed, but Mormon certainly gives only a brief account of what he saw and heard. Whichever it is, Mormon is doing it by commandment of the Lord. He is also sensitive to the reader’s feelings (v. 9).