Alma’s comment that “I do not glory of myself, but I glory in that which the Lord hath commanded me” echoes Ammon’s statement in Alma 26:12: “I will not boast of myself, but I will boast of my God.” Alma had recorded those words, and perhaps subconsciously echoed them here. His point is that there are many things that have happened that are good in spite of the terrible aftermath of the war. Even though Alma lamented those who died unrepentant, he recognizes that there have been many who have repented and come to God.
What Alma is doing in these verses is contextualizing the very real sadness associated with devastation with those things in which one might rejoice. There were many who died unrepentant, but there were many who came to God, and who would not have without the ministrations of the sons of Mosiah.
Their fathers were in captivity, a thing to be lamented. Jehovah saved them, something to be praised. The God of the Old World fathers delivered them from bondage to Egypt; that same God still has power to deliver them from bondage. While that happens at times as a release from physical bondage, the gospel also comes to release humankind from the bondage of sin that separates us from God.