Sixty-six years ago this week, US policymakers and President Truman made fateful decisions that meant the use of two atomic bombs against Japanese cities was almost inevitable—virtually unstoppable.  Film footage and other evidence of the true effects of the bomb were suppressed for decades.  We’ve been living with the nuclear after-effects ever since, from Hiroshima to Fukushima.

Starting yesterday, and related to publication of my new book and e-book Atomic Cover-up, I began offering a daily record of what transpired leading up the bombing of Hiroshima and Nagasaki in 1945. Yesterday we found Truman in his diary claiming that atomic bombs would only be dropped on military targets and not against “women and children.” Today we cover two major developments, from July 26, 1945. For more, including video, see my personal blog.

Early on July 26, Chief of Staff Gen.George Marshall cabled to Gen. Leslie Groves, military chief of the Manhattan Project back in Washington, DC, his approval of a directive sent by Groves the night before. It read: “1. The 509th Composite Group, Twentieth Air Force, will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki…. 2. Additional bombs will be delivered on the above tagets as soon as made ready by the project staff…..” This assembly-line approach would have tragic consequences for the city of Nagasaki. (Kyoto had been removed from the target list after the Secretary of War Henry Stimson pleaded that destroying this historic and beautiful city would really turn the Japanese against us in the postwar period.)

In a 1946 letter to Stimson, Truman reminded him that he had ordered the bombs used against cities engaged “exclusively” in war work. Truman would later write in his memoirs, “With this order the the wheels were set in motion for the first use of an atomic weapon against a military target.” Even years after the decision, and all the evidence (largely kept from the American people) that Hiroshima and Nagasaki were only partly “military” targets, Truman still acted otherwise.

The other major event from this day was equally significant. The Potsdam Declaration was issued in Germany by the United States, Britain and China. (The Soviet Union was still ostensibly not at war with Japan but agreed to enter the conflict around August 7. This has led some to suggest that we used the bombs quickly to try to end the war before the Russians could claim much new territory.) It was Truman’s first key wartime conference with other top leaders.

The declaration ordered Japan to surrender immediately and unconditionally or face a reign of ruin—“prompt and utter destruction”—although the new weapon was not mentioned (such a warning had been considered by Truman but rejected). Much was made of the importance of the “unconditional” aspect but three weeks later, after the use of the new bombs, we accepted a major condition, allowing the Japanese to keep their emperor, and still called the surrender “unconditonal.” Some historians believe that if we had agreed to that condition earlier Japan might have started the surrender process before the use of the atomic bombs. Others believe an explicit warning to the Japanese, or a demonstration of the new weapon offshore in Japan, would have speeded the surrender process. But the Potsdam Declaration set US policy in stone.

Greg Mitchell’s new book (also out as an e-book) is Atomic Cover-Up: Two U.S. Soldiers, Hiroshima & Nagasaki, and The Greatest Movie Never Made. He also co-authored, with Robert Jay Lifton, Hiroshima in America.

Like this blog post? Read it on The Nation’s free iPhone App, NationNow.