I think the third option would be a suitable answer.
Island hopping.
Because of the Pacific Islands
It was the use of the Atomic Bomb. Having won the war in Europe, the Americans
and their allies concentrated their efforts on the Far East. Japan refused to surrender despite the
on-going bombings and destruction of her army.
They also threatened to kill American POWs if they U.S. invaded Japan. Truman
ordered the use of the atomic bomb. It was
used in Hiroshima on August 6 then again on Nagasaki on August 9 resulting to
Japan’s surrender.
Don larson in 1956 i think