The land Desolation and the city Desolation are the focus of the battles described in Mormon 4. By review, the land Desolation was that land previously inhabited by the Jaredites (Alma 22:30, Ether 7:6). It was a land of large bodies of water and many rivers (Alma 50:29, Mosiah 8:8, Mormon 6:4).
A common misconception is that the land of Desolation was a desolate, barren wasteland. This is not true at all. The name refers to the desolation which came upon its inhabitants, And now no part of the land was desolate, save it were for timber; but because of the greatness of the destruction of the people who had before inhabited the land it was called desolate (Hel 3:6). There were many areas without timber apparently because the Jaredites cleared the land to build their cities, for the whole face of the land northward was covered with inhabitants (Ether 10:21). But we should not presume that the land was uninhabitable or inhospitable. Just because the timber was exceedingly scarce in 46 BC (Hel 3:5-10) doesn’t mean that it remained that way for the next four centuries. The land may well have replenished itself for we never hear of Mormon or Moroni complaining that the land northward lacked timber or that it was an inhospitable, barren land.
Nevertheless, the land Desolation would again earn its namesake—not because the trees would be chopped down but because the Nephites would be cut asunder and swept off…even as a dew before the sun (v. 18). The land Desolation would be the site of a Nephite “Desolation of Abomination.”