...Leo Szilard was a Hungarian scientist who had been driven out of Europe by Hitler's policies. He knew that uranium fission, recently discovered, might make a nuclear bomb possible, and he wanted to be sure Hitler didn't get it first. He labored to get scientists in the field to practice voluntary secrecy and keep their discoveries to themselves.
Then, he and a pair of fellow exiles, Eugene Wigner and Edward Teller, labored to get still another exile, Albert Einstein, to write a letter to President franklin Roosevelt, urging him to set in motion a secret project to build a nuclear bomb before Hitler did. Szilard knew that only Einstein possessed enough weight to be persuasive.
The letter was sent in 1941, Roosevelt read it, and, late in the year, he finally signed a directive that set up what came to be known as the Manhattan Project.
Now, he signed it on a Saturday, and our society being what it is, people are often reluctant to do anything on a weekend. I could imagine Roosevelt tossing his pen onto his desk on the particular Saturday and saying, with a touch of irritation, "The hell with it. Let's take it easy. I'll sign it first thing Monday." it would have been a natural thing to do.
Except he did sign it -- on Saturday, December 6, 1941. If he had waited till Monday, he might never have signed it, for Sunday, December 7, 1941, was Pearl Harbor Day; and,after that, by the time things cooled down, the whole business about the Manhattan Project might have been one with the snows of yesteryear.
What would have happened?...