"War is hell," summarized Civil War Union General William Tecumseh Sherman, whose scorched earth policy during his march through Georgia is credited with further weakening the Confederate army, ultimately shortening the war and saving lives. 

Eighty years later, during World War ll, the sentiments, tactics and strategy were still valid as President Harry S. Truman (D) authorized the first use of the atomic bomb on Hiroshima, Japan, 68 years ago today and another one on Nagasaki three days later.  The Japanese surrendered a week later. 

For those who still argue that this action wasn't necessary, mentioning the horrible deaths of the Japanese, (make no mistake, they were horrible) or the number of American troops saved (and they were) doesn't justify killing so many Japanese civilians, (the responsibility of a commander is to protect those under him as much as possible) or the Japanese were so weakened they were ready to surrender, (they weren't; they were the jihadis, suicide bombers, of their day) or other objections, Duncan Anderson of the British Royal Military Academy Sandhurst, which trains all British Army officers, offers another strong opposing opinion..

Utilizing "discoveries made upon the opening of hitherto restricted archives, and the work of British- and American-educated Japanese historians" and newly available information after the collapse of the Soviet Union, Anderson writes:

Also thanks to the work of Japanese historians, we now know much more about Japanese plans in the summer of 1945. Japan had no intention of surrendering. It had husbanded over 8,000 aircraft, many of them Kamikazes, hundreds of explosive-packed suicide boats, and over two million well equipped regular soldiers, backed by a huge citizen's militia. When the Americans landed, the Japanese intended to hit them with everything they had, to impose on them casualties that might break their will. If this did not do it, then the remnants of the army and the militias would fight on as guerrillas, protected by the mountains and by the civilian population.

But what about the passive, helpless Emperor Hirohito?  According to Anderson, he was not passive or helpless but the core of the Japanese military system,

[A]n all-powerful warlord, who had guided Japan's aggressive expansion at every turn. Hirohito's will had not been broken by defeats at land or sea, it had not been broken by the firestorms or by the effects of the blockade, and it would certainly not have been broken by the Soviet invasion of Manchuria, something the Japanese had anticipated for months.

What broke Hirohito's will was the terrible new weapon, a single bomb which could kill a hundred thousand at a time. Suddenly Japan was no longer fighting other men, but the very forces of the universe. The most important target the bombs hit was Hirohito's mind - it shocked him into acknowledging that he could not win the final, climatic battle.

As for the casualties

We now know that if the bomb had not been used, the invasion of Japan would have gone ahead. The best indication we have of the casualties that might have occurred are the actual figures for the eight-week campaign on Okinawa, in which 12,500 Americans died, and 39,000 were wounded.

Fighting at the same intensity (it could not have been less) on Kyushu and Honshu, campaigns which would have lasted some 50 weeks, would have produced 80 to 100,000 American dead, and some 300 to 320,000 wounded. Are these casualties enough to justify Hiroshima and Nagasaki?

If morality is based on numbers, and in this case it must be, then perhaps not. But what is usually overlooked in this numbers game, is the number of Japanese killed on Okinawa, which amounts to a staggering 250,000 military and civilian, about 20 Japanese killed for every dead American. If we conduct the same calculation for an invasion of the Japanese Home Islands, we arrive at a figure of at least two million Japanese dead.

Let's repeat that.  Using  the ratio of American dead to Japanese dead, if American troops had undertaken a conventional  invasion of Japan instead of dropping the bomb "we arrive at a figure of at least two million Japanese dead."  And 100,000 dead Americans. 

Anderson concludes

The losses in Hiroshima and Nagasaki were terrible, but not as terrible as the number of Japanese who would have died as the result of an invasion. The revisionist historians of the 1960s - and their disciples - are quite wrong to depict the decision to use the bombs as immoral. It would have been immoral if they had not been used.

War is still hell.