Alma reports that "in the sixteenth year of the reign of the judges . . . there began to be continual peace throughout all the land (Alma 30:2). Yet, the reader will soon find that there were "wars between the Nephites and the Lamanites in the eighteenth year" (Alma 43:4), a difference of only two years. One might wonder how two years could be considered "continual peace." Matthew Roper notes that here the Book of Mormon, just like the Bible, uses the term "continual peace" to specify an uninterrupted duration of time (in this instance, uninterrupted by strife and conflict). A similar use of the term "continual[ly]" can be found in Genesis where the flood waters "returned from off the earth continually" (for 150 days) and "decreased continually until the tenth month" (Genesis 8:3, 5). [Matthew Roper, Book Review in Review of Books on the Book of Mormon, Vol. 4 1992, p. 90]
“Continual Peace Throughout All the Land”
According to Brant Gardner, the phrase "continual peace" is characteristic of Mormon's abridgment, and is not found in the small plates material. While the general meaning is obvious, the duration of "continual" changes dramatically. For instance, in Mosiah 19:29, Limhi has "continual peace" for only two years. Here we have continual peace assigned to the sixteenth year, and then assigned to the seventeenth year. Therefore we might assume that "continual peace" applies to year periods and it is used when there is a lack of armed battle, or of internal contention. One should note that there will be two years of peace, and the next event that Mormon will list that disturbs that peace is the arrival of Korihor. For Mormon, Korihor appears to be a disruption of peace just as was a war. [Brant Gardner, Book of Mormon Commentary, [http://www.highfiber.com/~nahualli/LDStopics/Alma/Alma30.htm], p. 3]
The People Did Have No Disturbance in the Sixteenth Year
According to Brant Gardner, it is interesting that Mormon makes note of a year in which there seems to be nothing worthy of abridging. He states, "the people did have no disturbance in the sixteenth year of the reign of the judges over the people of Nephi. And it came to pass that in the commencement of the seventeenth year of the reign of the judges, there was continual peace. As far as Mormon's use of these yearly chronicles is concerned, it is worthy of note that such a yearly scheme is known from the textual Anales de Cuauhtitlan, as well as being clearly indicated by the structure of the various Mesoamerican codices. Moreover, the Anales de Cuauhtitlan gives years during which nothing is recorded. Thus even in the absence of information, Mormon appears to be following a scheme that is known from at least one Mesoamerican historical document. [Brant Gardner, Book of Mormon Commentary, [http://www.highfiber.com/~nahualli/LDStopics/Alma/Alma30.htm], p. 4]