Did the United States have to drop the bomb?

Thousands of New York Times readers have responded to a request, 70 years after the attacks on Hiroshima and Nagasaki, to consider the argument that started at the dawn of the atomic age and has found little consensus since.

“Seventy years later, we do not and can not know,” writes Gwen Boucher from Portland, Ore. “Hopefully the world knows these weapons can not be used again.”

Another reader, Elaine Ledwon from Ann Arbor, Mich., cautions: “It is unfair to judge the dropping of the bomb from a 2015 perspective.”

Still, many readers, drawing on the perspective and historical knowledge about what was happening at that time in the war offered cogent justifications, condemnations, indictments and explanations.