In verses 5 and 6, Samuel the Lamanite uses a common prophetic device known as a “war oracle.” “War oracles” are prophetic warnings to the people that God’s “army” will be coming after them. The words “army” and “host” are often used interchangeably in these pronouncements. The phrase, “Lord of hosts,” is the name used for God when he is standing ahead of his army and his legions of angels who are coming to cleanse the earth and to vindicate the righteous and judge the wicked. Scholars identify phrases like “sword of justice,” “fierce anger,” and “Lord of hosts” as characteristic language in war oracles. In chapter 13, but only in that opening chapter, Samuel speaks three times of “the Lord of Hosts” (13:17, 18, 32).
Book of Mormon Central, “How Can People Today Avoid Being Destroyed Like the Nephites Were? (Helaman 13:5–6),” KnoWhy 327 (June 16, 2017).