The United States of America exploded an atomic bomb over Hiroshima on August 6, 1945 and over Nagasaki on August 9th. While both cities in Japan hosted military bases, the vast majority of causalities were civilians. An estimated 150,000 died at Hiroshima including 20,000 soldiers and 20,000 Korean laborers. About 80,000 died at Nagasaki, and while military manufacturers were destroyed, relatively few soldiers died there.
One of the most basic ideas of war crimes law is that the purposeful killing of civilians is a war crime. Yet most Americans believe that the atomic bomb use was justified in this case (the only use of atomic bombs other than for testing, ever, in world history.)
The typical American defense against charges of war crime is that it saved the lives of large numbers, potentially millions, of American soldiers who would have died if Japan had been conquered by conventional means. Is it therefore not a war crime to kill civilians if that achieves military objectives like decreasing military casualties? Other, often better, defenses against the war crimes accusation will also be considered here.
Some background information will be useful in this discussion. The war between Japan and the United States began in 1854 when a U.S. fleet of warships under Commodore Perry seized Okinawa and then used the threat of further force to induce the rulers of Japan to end their long commitment to isolation and peace [See Okinawa, Commodore Perry, and the Lew Chew Raid]. Relations varied over the following decades, then disintegrated in the 1930s when the U.S. continued to support the right of itself and European nations to have colonies, economic spheres of influence, and puppet governments in Asia, while denying that Japan should be able to play by the same rules.
Before the war began President Roosevelt gave numerous speeches condemning nations that dropped bombs from warplanes into cities. He demanded that all nations refrain from targeting civilians.
Rather than capitulating to demands from the U.S. that Japan become a third-rate power again, and watching the rapid building of a vastly superior navy, air force, and army in the U.S. in 1940, the Japanese military and the government they controlled decided to gamble on a first strike, which took place at Pearl Harbor, Hawaii on December 7, 1941 [See Pearl Harbor, China, and The Cable].
There is no denying that, before the atomic bombs were dropped, Japan was losing the war. Yet President Harry Truman and most U.S. military leaders did not feel the war was going particularly well. While the U.S. had overwhelming sea and air power, the Japanese had adapted their ground defenses to minimize that advantage. At the Battle of Okinawa alone the U.S. had lost 49,151 soldiers. Estimates of U.S. deaths from conquering Japan started at around 1 million, and that was probably a very conservative number. While nothing compared to the 11 million Communist soldiers who had died fighting Adolf Hitler's army, it was a dismaying number to Americans who were tired of war.
Politically, President Truman's hands were tied. His predecessor, Democratic Party kingpin President Roosevelt had demanded unconditional surrender from Japan. When the a-bombs were ready Truman repeated that demand in the Potsdam Declaration. The Japanese had always been open to a negotiated peace, even before the war began, but had never been willing to surrender unconditionally. Up until then no nation in Japan's position (still holding its mainland, many Pacific islands the U.S. military had "hopped" over, most of China and all of Korea) had ever been expected to surrender unconditionally. It was against the basic understanding of the laws of nations and what it means to lose a war.
The well-documented Japanese military's position was they would surrender if they could disarm themselves, withdraw their troops from China, and try their own war criminals. The peace faction in Japan, including the Emperor and his civilian advisors and even a significant portion of the military, were willing to surrender with one condition, that the Emperor remain the official sovereign of Japan.
Truman and his advisors (all Democratic Party leaders) were aware that if the bombs worked there would be significant civilian casualties. Their reasoning was simple: they did not want to fight the Japanese in what had always been the honorable method. The war might go on until 1948, or the U.S. might suffer a reversal and never win. Or the citizens of the U.S. might have urged their congressmen to negotiate a peace. For the record, two Republican Party generals, Dwight Eisenhower, commander of U.S. forces in Europe, and Douglas MacArthur, commander of U.S. forces in the Pacific, were against using the atomic weapons on cities as they correctly believed it would be a dishonor to U.S. military forces.
The disposition of colonies was also a prime consideration. If the U.S. had fought a long war with Japan while the British Empire, French Empire, Russian Empire, and other European nations had a chance to rebuild their commerce, the U.S. might not have been able to dominate the world stage in the 1950s and 1960s.
There is no loophole in the official war crimes laws allowing the purposeful killing of civilians. Even collateral damage, the incidental killing of civilians when fighting enemy soldiers, is supposed to be minimized. If you argue that, for instance, it is okay to kill civilians in order to reduce the deaths of one's own soldiers, there is no line that can be reasonably drawn to protect the innocent. Civilians always provide the economic support for soldiers in war, willingly or unwillingly. Wipe out a work force, and no one is around to build tanks. To subscribe to the theory of total warfare is to say that there is no such thing as a war crime.
Is there a permissible level of killed civilians? Killing civilians accidentally is considered a hazard of war, but at some point should it be clear that accidental is really on purpose. If one civilian dies in an engagement where 100 soldiers are killed, that is not good, but unless the civilian was specifically targeted we tend to not see a war crimes. But where do we see a war crime? A ration of 10 to 100? 50 to 100? 200 to 100? At Hiroshima the ratio was closer to 750 to 100, at Nagasaki even higher. A reasonable person can only conclude that the point was to kill massive numbers of civilians, and the military targets at the city merely provided a pretext. U.S. records support that interpretation.
Truman and crew did not honestly subscribe to the theory that the war crimes laws are ridiculous. They prosecuted and executed a few Germans and a lot of Japanese for war crimes after the war. They turned the Rule of Law into the Gruel of Law: the war crimes of victors would not be war crimes, only losing nations had committed war crimes.
An alternative defense is that only aggressor nations should be subject to war crimes law. This position creates much trouble. It is a not always clear which nation is the aggressor. Often two nations or sets of nations are eager for war, and the incident that sets of the war is almost irrelevant, as in World War I or the War of 1812. But again, you need to ask: is it okay to kill women and children, even of an aggressor nation? And when nations have been at war at intervals for centuries, is the aggressor label awarded based on the latest round, or is there some more complex calculus that should be used?
If aggressor nations are the only ones that must obey the rules of war, the whole exercise in war crimes law is probably pointless. Starting a war is itself a violation of the rules of war (although as usual, there are economic acts of war, like blockading a nation, that might justify calling a war defensive, or a war of survival). Having violated that rule, why follow any of the rules, unless they offer some sort of advantage?
Finally, there are racial arguments. U.S. relations with Japan had a huge racist component from the very beginning. Official discrimination against Japanese was a constant of U.S. domestic policy until after World War II. Destroying (perceived) subhuman lives in order to spare (white) human lives was a significant factor in World War II, but it should be no excuse in a war crimes tribunal.
Conclusion. A fair and impartial person should be able to identify the atomic bombing attacks on the Japanese cities of Hiroshima and Nagasaki as war crimes. The excuses given for the war crimes should be rejected as based on racism, nationalism, cowardliness, and a criminal mindset. The war criminals responsible should have been tried and sentenced. The organizations the war criminals led should have been disbanded.
Further, the failure to fairly uphold the war crimes laws subsequently led to contempt for those laws by the political and military leaders of the United States of America and their allies.