As momentous events like the fall of France in 1940 recede ever further into the past, they may lose their power to stir up passions, and even their capacity to provoke wonder, but all the while the scope for intellectual rigour in explaining what happened ought to be expanding in three dimensions. First of all, one comes to see how the basic elements of the historical situation in question developed in succeeding years (and perhaps to see more clearly how they had developed in the preceding eras as well); this, of course, represents the proverbial advantage of hindsight. Beyond that, new analytical approaches – in many cases worked out by those trying to come to grips with more recent phenomena – may be turned to the purposes of historical understanding; the historian is then in a position to transcend the terms in which participants and observers in the past thought. And, not least, the evidence that one can bring to bear on the events becomes much more copious as the relevant archives open up.

In all three of these respects, historians have today reached an especially propitious point from which to reconstruct the French military road to defeat in 1940.