Question

Supporters of using the atomic bomb at the end of World War II believed that
Japan might win the war if the bomb was not used.
Americans were tired of war and the US should end it quickly.
Russia was developing a bomb and the US needed to use it first.
Japan was developing a bomb and the US needed to use it fi

Answer 1

The beliefs held by supporters were mainly:
- Americans were tired of war and the US should end it quickly. (Yes — a major justification: use the bomb to force a rapid Japanese surrender and avoid a costly invasion.)
- Russia was developing a bomb and the US needed to use it first. (Sort of — supporters wanted to demonstrate U.S. power and limit Soviet influence in Asia; there was concern about the USSR’s future nuclear capability and political ambitions.)

These were not held by supporters:
- Japan might win the war if the bomb was not used. (No — Japan was militarily and economically exhausted; the concern was that Japan would not surrender without a decisive shock and that an invasion would cause huge casualties, not that Japan would actually win.)
- Japan was developing a bomb and the US needed to use it first. (No — Japan did not have a credible atomic program comparable to the Manhattan Project.)

In short: the main pro-bomb arguments were ending the war quickly and shaping postwar power (especially vis‑à‑vis the USSR), not fear that Japan would win or that Japan had its own nuclear weapon.