Answer:
Even though this is a very debatable topic, the U.S. might have been justified.
Explanation:
Truman decided to drop the 2 atom bombs after Japan refused to surrender. To summarize a very long and detailed topic, after many hours and days of thinking, he decided to drop the bombs. If he hadn't dropped the bombs, they would have had to invade Japan and could have lost far more people than dropping the bombs. Furthermore, Japan would have most likely not surrendered from a ground or sea attack.
The leader of Japan actually did not want to surrender even after the bombs were dropped and tens of thousands of people were killed but was persuaded by officials who realized that they had lost.
This descison will always remain a highly debated topic because there are two sides to see to this. This can be a highly debatable topic to discuss, but this is my opinion.
Hope this helps!