Final answer:
Emperor Hirohito's intervention and acceptance of unconditional surrender after the atomic bombing of Nagasaki, influenced by prior events, best indicates the importance of the atomic bombings in ending WWII.
Step-by-step explanation:
The detail from the passage which best supports the notion that the atomic bombings were a significant factor in Japan's surrender is: "Even before the atomic attacks, the conventional bombings of Japan, the defeat of its forces in the field, and the entry of the Soviet Union into the war had convinced the Imperial Council that they had to end the war. They had hoped to negotiate the terms of the peace, but Emperor Hirohito intervened after the destruction of Nagasaki and accepted unconditional surrender." This statement underscores the cumulative effects of the conventional bombings, military defeats, and Soviet entry into the war which all pressured Japan towards capitulation, but it was the unprecedented destruction wrought by the atomic bombs that finally prompted Emperor Hirohito to intervene and accept unconditional surrender, thus bringing an end to the war.
Some say it was right because it ended the war quickly instead of dragging it out for months or even years; others say it was wrong because it killed so many innocent civilians and caused too much long term damage. (paragraph 12)
This detail supports the answer because it highlights the controversial nature of the decision to use nuclear weapons on Japan. It shows that there are differing opinions on whether the use of atomic bombs was justified or not, based on the speed of ending the war versus the loss of innocent civilian lives and long-term damage caused.