The inventors never really cared about anything...it's all about money.
You could check with history about nuclear weapon, it has alot of info.
Nuclear weapon has became effective to end of WWII after Japan realized over 2 atomic bombing has dropped and destroy the couple of cities, it's very terrible and many people got cancer or illness due radiation and US went surrender of Japan (became military occupied) until early 1950's. Today, Japan is just doing great and have alot of high tech stuff and advance in economy.
Without nuclear weapon, it would probably be divide the Japan into north and south, USSR would attack and takeover North Japan since US and allied would takeover South Japan, after that, USSR could put communism in North Japan, just similar to Korea, divide into North Korea and South Korea. I don't want see North Japan to be under communism and seems so horrible, however it never happen because we already surrender of Japan since USSR was annex the few area to their country.
Right after WWII is over isn't exciting or peace because we had been in cold war for almost 50 years, it was so terrible and we never know that world could be end if USA and USSR start war against around them, also we were fear of communism extension, such as Vietnam, Laos, Afghanistan and Cuba, South Korea could be annex with North Korea to become Korea with brutal communist rule but we already save South Korea from annex with North Korea, however we fail to save South Vietnam and Cuba from become communism.