As published in the Chicago Daily News, sister publication of the Chicago Sun-Times:
Chicagoans likely spent Aug. 6, 1945, reading every piece of news they could find. That day, the U.S. dropped the first atomic bomb, a brand-new weapon never used in warfare before, on Hiroshima, Japan.
The Chicago Daily News devoted most of the front page to the news of the bomb, covering the attack itself, statements from President Truman and even explanations and photos of how atomic energy worked — and how destructive it could be.
“An atomic bomb, hailed as the most destructive force in history and as the greatest achievement of organized science, has been loosed upon Japan,” the main story from the Associated Press declared. “President Truman disclosed in a White House statement today that the first use of the bomb — containing more power than 20,000 tons of TNT and producing 2,000 times the blast of the most powerful bomb ever dropped before — was made 16 hours earlier on Hiroshima, Japanese army base.”
The bomb fell on the city at about 6:20 p.m. Chicago time the previous day, the paper reported, which would have been about 8:20 a.m. in Hiroshima. Roughly 318,000 people lived in the city at the time.
Truman and Secretary of War Henry Stimson argued the bomb was the only answer to Japanese leaders’ refusal to surrender, the paper said. “The President noted that the Big Three ultimatum issued July 26 at Potsdam was intended ‘to spare the Japanese people from utter destruction’ and the Japanese leaders rejected it.”
To give readers an idea of the bomb’s power, the paper ran a separate story about a test bomb dropped on July 16 at the Alamogordo Air Base, which sat about 120 southeast of Albuquerque, New Mexico. That first test “immediately vaporized a steel tower from which the weapon was suspended and sent a massive cloud billowing into the stratosphere with ‘tremendous power,’ the War Department said today.”
An official description of the test drop read:
“At the appointed time, there was a blinding flash lighting up the whole area brighter than the brightest daylight. A mountain range three miles from the observation point stood out in bold relief. There came a tremendous sustained roar and a heavy pressure wave which knocked down two men outside the control tower (10,000 yards from the explosion). Immediately thereafter, a huge multi-colored surging cloud boiled to an altitude of over 40,000 feet. Clouds in its path disappeared. Soon the shifting stratosphere winds dispersed the narrow gray mass. The steel tower had been entirely vaporized. Where the tower had stood, there was a huge sloping crater.”
Other stories in the paper that day detailed the bomb’s creation, how scientists first split the atom and the late President Roosevelt’s cooperation with United Kingdom Prime Minister Winston Churchill that led to the bomb.
In his explanation of how atomic energy worked, staff science writer James C. Leary called out University of Chicago physicist Prof. A.J. Dempster, who “succeeded in isolating certain uranium atoms called Uranium-235” in 1935. That discovery allowed physicists five years later to bombard the U-235 samples with hydrogen atoms and find that, through the process, “it was possible to get ... tremendous amounts of energy.”
Following that discovery, “the federal government’s blackout descended on the whole process, as its importance in the war became obvious, and nothing more has been made public,” Leary wrote.