The Lamanite/Gadianton army forced the Nephites from Jashon, and apparently allowed them to stop in Shem. This is implied by the “began to come upon us again,” which indicates a renewal of attack. Since the attack could not be renewed unless it had stopped, it would appear that we may have an indication of another season cessation of warfare. In this case, it would be on account of the rainy season when warfare was difficult. The Lamanite/Gadianton army had no incentive to press through difficult physical conditions if they could so easily remove the Nephites at will. Therefore, it is plausible that this is the cessation for the rainy season.
Chronological: The three hundred and forty sixth year would be 336 A.D.
“They Began to Come Upon Us Again”
The respite at Jashon is short-lived. They are driven from that position in the very same year. This suggests that they were able to take a few months off, and then the warfare begins again. It is tempting to see this break as governed by the seasons rather than militaristic concerns. If they are driven at the ending of the year, it is probable that warfare ceased because both sides took time to harvest crops. The pursuing Lamanite/Gadianton army required food as well as the Nephites. The Lamanite/Gadianton army had no reason to need to press the attack, for they could apparently move at will. Therefore, stopping for harvest and reprovisioning makes complete sense, particularly given the seasonal pattern of warfare. Sorenson notes:
“Our information on the timing of warfare in this area has not been examined comprehensively by scholars. What is known is consistent, for example, with the fact that in Yucatan, wars were usually fought between October and the end of January (or February in other Mesoamerican regions). In that period, travel was rarely restricted due to bad weather; it was still relatively cool, and food was available either by supply from the logistical base or by taxing the subjugated.
The schedule varied slightly depending on local topography and climate. The corn crop, fundamental in the diet everywhere in Mesoamerica, is typically planted in April or May, just before the rains begin and after the fields have been cleared and the rubbish burned. It can be harvested about the time when the clouds and rain taper off (the wettest months are July and September for most regions) and the temperature rises because of greater sunshine. Harvest is from October to December, again depending on locality and on crop variety.
The crucial time for agricultural labor under this regime is, and was anciently, March through May. At other times, being away was inconvenient but not critical. Probably the segment of time freest from field work for the typical cultivator/warrior was November through February, which, of course, coincides with the war season. Under emergency conditions, naturally, some military action could go on, though hampered, throughout most of the year. (John L. Sorenson. “Seasonality of Warfare in the Book of Mormon and in Mesoamerica.” Stephen D. Ricks and William J. Hamblin, eds., Warfare in the Book of Mormon [Salt Lake City and Provo: Deseret Book Co., Foundation for Ancient Research and Mormon Studies, 1990], 456.)