Most people, certainly most physicists were aware that war between Germany and the Western powers was imminent, and it did break out early September of '39. America entered it only two years later in December of '41, but American scientists generally were very much aware of it and so voluntarily they gave up their normal research and in large numbers volunteered to do work useful for the war effort. The most important effort was for the Radiation Laboratory at MIT, Massachusetts Institute of Technology, which brought together, I think, probably the best experimental American physicists and a few theoretical ones to explore the possibilities of radar. In this they followed the pioneer work that the English had done making radar useful for... in war and making it possible by radar to blunt the Nazi attack on England in the fall of 1940. The real impetus to this war work came in the summer of 1940 when the Nazi armies overran all countries in Western Europe that they were attacking. First of course - not in Western Europe - Poland, but then in Western Europe all the smaller countries and finally France. Everybody had expected that France would be a very strong country and could resist the Nazi aggression, but it turned out that France fell within a few weeks, and this gave a terrible shock to the people, both in England and the United States, seeing that the Nazi armies were essentially irresistible. We all knew that Nazi Germany completely overturned the Western values, so it was not just a defense of nationality, but it was a defense of the values which had grown up in the Western world since the Renaissance - 400 years. And it was this which made American scientists volunteer to do war work. Now war work by scientists, of course, was not a new thing at all. It goes back to antiquity when Archimedes of Syracuse defended the city of Syracuse against the Roman power with his inventions which were very ingenious inventions to combat a powerful army by use of his scientific knowledge.