What new weapon made allied leaders worry about the cost of invading the japanese mainland?

it was the atomic bomb that made allied leaders worry about the cost of invading the japanese mainland, since they knew the japanese would continue to fight without it.

by the end of wwii, american leaders thought that the only way to defeat japan would be by means of an invasion to the island. the allied leaders became worried about the cost of invading japan by land, since they believed they could lose more than a million us soldiers. as a result, the american president truman decided to use a new weapon, which was the atomic bomb. on august 6th, in 1945, the first atomic bomb was dropped on hiroshima, japan, killing thousands of people. but japan did not surrender until the second atomic bomb was dropped on nagasaki.

the answer is b: an economic crisis throughout the country.

i would say it is the roman empire europe after the norman conquest.