In the thirtieth year of the reign of the judges, Helaman sends a letter to Moroni to inform him of the actions of Helaman’s two thousand stripling warriors, who had begun their service at the end of the twenty-sixth year (see the comments on Alma 53:23). Thus, the contents of this letter reflect on the previous four years, but it was either written or received early in the thirtieth year.
The implication of this letter is that communication was difficult, from where Helaman and his unit were serving, to where Moroni directed his armies.