In 1945, the US was the most Christian nation in the world (that is, if you can label as Christian a nation whose churches overwhelmingly fail to sincerely teach or adhere to the ethics of Jesus as taught in the Sermon on the Mount).
Prior to the bomb exploding over St. Mary's Urakami Cathedral on 11:02 AM, Nagasaki was the most Christian city in Japan. The Nagasaki cathedral was the largest Christian cathedral in the Orient.
Those baptized and confirmed Christian airmen, following their wartime orders to the letter, did their job efficiently, and they accomplished the mission with military pride, albeit with any number of near-fatal glitches. Most of us Americans in 1945 would have done exactly the same if they had been in the shoes of the Bock's Car crew, and there would have been very little mental anguish later if we had also been treated as heroes.
Nevertheless, the use of that monstrous weapon of mass destruction to destroy a mainly civilian city like Nagasaki was an international war crime and a crime against humanity as defined later by the Nuremberg Tribunal.