Question

What new weapon made Allied leaders worry about the cost of invading the Japanese mainland?

Answer 1

atomic bombs is your best answer

The atomic bomb didn't make the Ally leaders worry at all, but they were looking for an alternative from invading Japan, which would have costed thousands of lives, and trillions of dollars. Instead, the atomic bomb was the best solution, even with radiation fallout.

hope this helps

Answer 2

Answer:

the answer is

Kamikaze fighter