The slogan - No More Hiroshimas
"No More Hiroshimas." It appeared on the front page of the Chugoku Shimbun on August 1, 1948, three years after the atomic bombing. The article stated that "The city, which was said would be barren earth for 75 years, has begun rising again as a city of peace with a cry of 'No More Hiroshimas!'" At the memorial ceremony on August 6 that year, this slogan, using the plural form, was displayed in English on a large sign.
the first "No More Hiroshimas" appeared in an article of the Pacific Stars and Stripes, a newspaper published for U.S. military stationed abroad, on March 5, 1948. The article notes that Reverend Kiyoshi Tanimoto of Nagarekawa Church in Hiroshima called for a campaign to make August 6 "World Peace Day" with the hope that there would be "no more Hiroshimas."
This article was written by a reporter for United Press International, Rutherford M. Poats. Mr. Ubuki says it was the oldest mention of "Hiroshimas" among all the references he could confirm.
It seems the truth is that after the article by Mr. Poats appeared, a group led by Rev. Tanimoto developed the "No More Hiroshimas campaign" to establish August 6 as a day of remembrance. As the campaign grew, the slogan spread.