The problem that Coriantumr didn’t realize was that, while he was presented with a weakened center, there were still large Nephite armies assigned to the borders. Thus, as Coriantumr presses toward Bountiful, Moronihah (Moroni’s son and successor) sends reinforcements to Bountiful under the leadership of the seasoned general, Lehi. This created a defensive army sufficiently strong that Coriantumr’s forces were defeated and forced to retreat toward Zarahemla. This would place them in a center city where they could be easily surrounded. This invasion was essentially defeated, even if it was not yet over.