To render the sprawling activities of WWII palatable to digestion (because even the most devoted of readers have their limits) the tendency of authors is to show the war as seen through the eyes of the Great Powers and the Great Men.
And as seen through the eyes of those wisest of Wise Men, the scientists.
A commensal history of 1939-1945 should also start with a war between a handful of Great Men and Great Powers, because that is the way it all began.
But, to be fully accurate, it should also end in a confused co-mingling of the actions of the decisive small as well as those of the chastened great.