The atomic bomb was necessary to end the war with Japan at the earliest possible moment. By the early summer of 1945, Japanese leaders knew they could not win. But they fought on in hopes of securing better surrender terms.
President Harry S. Truman considered several ways to convince Japan to quit the war: 1) intensifying the already heavy bombing of Japanese cities; 2) waiting for the Soviet Union, an ally in defeating Germany, to join the war against Japan; 3) allowing Japan's emperor, Hirohito, to remain on his throne; and 4) invading Japan.
The first three options were far from certain to compel a Japanese surrender quickly, however, and each posed serious military, political, and diplomatic risks. More than 55,000 Americans had already died fighting the Japanese in the Pacific. An invasion was certain to be very costly in American lives.
When the atomic bomb became available in July 1945, it appeared to be the most promising way to end the war as soon as possible and without the drawbacks of the alternatives.
The atomic bombing of Hiroshima and then Nagasaki persuaded Emperor Hirohito, who had wavered for weeks, that the war must end immediately. Combined with the Soviet entry into the conflict, the atom bombs brought about Japan's surrender within a few days.
The bomb was necessary to accomplish Truman's primary objectives of forcing a prompt Japanese surrender and saving American lives, perhaps thousands of them.
J. Samuel Walker, Author
Prompt & Utter Destruction: Truman and the Use of Atomic Bombs Against Japan
When General Dwight D. Eisenhower, then the Supreme Allied Commander, was informed by the Secretary of War that the atomic bomb was going to be used, he later recalled saying it was unnecessary because Japan was already largely defeated. Eisenhower said the bomb was "no longer mandatory as a measure to save American lives." At one point after the war he said bluntly, "It wasn't necessary to hit them with that awful thing."
Before the bomb was used, U.S. intelligence officials believed the war would likely end when two things happened: When the U.S. let Japan know their Emperor could stay on as a figurehead, and when the Soviet army attacked. The U.S. did tell Japan the Emperor could remain, and the Soviets declared war, as agreed, on August 8.
But U.S. officials chose not to test whether this intelligence was correct. Instead, Hiroshima was bombed on August 6, and Nagasaki on August 9. Because of logistics, an invasion of Japan could not begin for another three months, so the U.S. could have waited to see if Japan would surrender before dropping the atomic bombs.
Most top World War II military leaders are all on record agreeing with Eisenhower. Admiral William Leahy, President Truman's Chief of Staff, later called the bomb a "barbarous weapon" that was unnecessary. Leahy wrote, "The Japanese were already defeated and ready to surrender. . . . In being the first to use it, we . . . adopted an ethical standard common to the barbarians of the Dark Ages."
Professor of Political Economy
University of Maryland