This is the most important reason for Americans to remember what they call the Vietnam War, the fact that it was one conflict in a long line of horrific wars that came before it and after it. This war’s identity—and, indeed, any war’s identity—cannot be extricated from the identity of war itself.
-- Viet Thanh Nguyen (Prologue paragraph 2)

Importance: This demonstrates that wars have no fixed end, but are continuous streams of violence. It also explains why Nguyen uses the term "the war."

Nations cultivate and would monopolize, if they could, both memory and forgetting. They urge their citizens to remember their own and to forget others in order to forge the nationalist spirit crucial for war, a self-centered logic that also circulates through communities of race, ethnicity, and religion.
-- Viet Thanh Nguyen (Just Memory paragraph 1)

Importance: This demonstrates that nations have an interest in cultivating a preferred collective memory to justify future wars and the national identity.

For majorities...
-- Viet Thanh Nguyen (chapter 1 paragraph 2)