The rst test explosion was codenamed Trinity, and the documentary was called The Day After Trinity. What was believed in 1945 to represent a long term, decided military advantage for the United States turned out to be an illusion, much as Oppenheimer likely suspected. A reaction paper is typically a 2-5 page document in which the writer responds to one or more texts. I truly believe they had no real alternative but to complete the job their government had asked them to do. Response to The Day After Trinity By David Elhard.