Brant Gardner notes that for many years the prevailing scholarly opinion of the Mesoamericans was one of peaceful stargazers, in no need of fortifications. Therefore the notion that the Book of Mormon should describe fortification of cities was taken as a proof against the text. However, more recent work has shown that this is no anachronisms, and that fortifications fit into the Mesoamerican political framework.
In a study of the extant archaeological literature on the subject, fortifications were listed by time period. The reader should keep in mind that these numbers are not comprehensive since they depend on the accidents of discovery. A chart lists the following totals of fortified and defensive sites created within the period:
Time Period Definite Possible
Early Pre-Classic (pre-1000 B.C.) 0 1
Early Middle Pre-Classic (1000-600 B.C.) 0 2
Late Middle Pre-Classic (600-400 B.C.) 5 1
Late Pre-Classic (400-50 B.C.) 30 2
[John L. Sorenson, "Fortifications in the Book of Mormon Account Compared with Mesoamerican Fortifications," in Warfare in the Book of Mormon, p. 429]
Note* Jarom would have lived around 399 B.C.