U.S. President Barack Obama's historic visit to Hiroshima later this month, the first ever by a sitting president, has rekindled the debate on both sides of the Pacific on what happened during the weeks leading up to the Aug. 6, 1945, atomic bombing of the city in the closing days of World War II.

Aside from calls for the president to apologize — or not apologize — for the decision made by his predecessor, Harry Truman, 71 years ago, and endless speculation about what the visit means for current politics (read: the fortunes of Shinzo Abe in July's Upper House election and the fortunes of Hillary Clinton and Donald Trump in November's U.S. presidential election), Obama's visit has amateur and professional historians everywhere reviewing the fateful decisions in Tokyo and Washington that led to the bombing.

And, for Kyoto and Osaka, it was indeed fate, and the deliberations of a few men at the highest levels of the American government, that spared both cities from a similar bombing.