This isn't a popular view, but it is fact. Japan belived the USA was not negotiating in good faith over the issues of the Japanese war in China (and frankly we weren't). Either the American Secretary of State or the Secreatary of Defence stated before Pearl Harbor, "We will have war with Japan if we have to start it ourselves" should give you and idea of the government's attitude toward Japan. The USA cut off all oil supplies to Japan. The Japanese fully believed the USA was trying to destroy the Japanese economy. They felt their only hope for national survival was to move south and seize the oil fields in Sumatra etc. They knew this meant war with the US. So the only logical step in their minds was to attack the US fleet at Pearl. Read John Tolland's Rising Sun for more on this.
It was the President decision to end the war and collapse Japans means to make war.
Truman
Not letting the soldier and sailor go in Japans mainland since it would be more war casualties for the US than the one they had already.
== == The final decision was made by the US President at that time, who was Mr Truman.
President Harry S. Truman made the decision to use the atomic bomb on Japan to end WW II
Harry S. Truman
That decision was not made by a group of persons, it was Truman who decided it.
This decision was made to avoid the higher casualties caused by an actual invasion .
The hydrogen bomb.
Harry S. Truman.
The US .
US