Atomic bombs were invented in the summer of 1945, in the United States. The Manhattan Project — the project that was tasked with the creation of the bomb — tested the first atomic bomb on July 16th, 1945.
Just a few weeks after, on August 6th, America dropped two atomic bombs on Hiroshima and Nagasaki in Japan. Many people debate whether President Truman was justified in dropping the two atomic bombs. However, President Truman was fully justified in dropping the bombs. He was justified because it caused a swift end to the war, saved American lives, and allowed the U.S. to have more negotiation power. First, dropping the atomic bombs on Hiroshima and Nagasaki caused a swift end to the war.
President Harry Truman could have either dropped the bombs or invade Japan, as those were the only viable options at the time. President Truman opted to drop the atomic bomb because it would end the war quicker than invading Japan, as well as saving many lives. The U.S. was reasonable to take into account the death count, and they clearly saw casualty estimates for an invasion, too.
Lastly, if we had invaded Japan, we would have firebombed their cities anyways, to cut off their supplies. Speaking of death counts, bombing Japan ended up saving many American lives. Estimates say that conquering Japan would cost 1.7–4 million American casualties, including 400,000–800,000 fatalities, and five to ten million Japanese fatalities.
According to the National WWII Museum, the U.S. only suffered 418,500 casualties in the entirety of WWII, and Japan suffered three million. That would mean that an invasion of Japan would over double the number of U.S. casualties, and over triple Japan’s casualties.
That is over 3% of the entire world population at the time (estimated at two and a half billion). It is also said that Japan was prepping their citizens with the mantra to fight until the last man. This would have made it difficult for the Allies to get Japan to surrender.
According to the Atomic Heritage Foundation, Hiroshima had thousands upon thousands of warning leaflets dropped on them, warning them of what would happen. The leaflets both told civilians to evacuate and occasionally asked for Japanese citizens to push their leaders to surrender. Although Japan was weakening, and their supplies were dwindling, “there was reason to believe that Japan would never surrender and that an invasion of the main Japanese islands would result in staggering U.S.