[JollyElm]

(I'm going to take a pseudo-intellectual approach to the topic...)

Everything is always about hindsight. Looking back, it is generally accepted that WWII 'began' in 1939. However, if you took a time machine back to 1939, I highly doubt the events going on were thought of as a full scale war to the vast majority of the world. Since (as I'm sure others have noted) we know how the war escalated, eventually consumed the planet, and finally came to an end in 1945, finding the true beginning is nothing more than a scholarly pursuit. But since the US is the center of the baseball card collecting universe, WWII began for us on December 7, 1941 (FDR/Congress declared it as such the following day). So, unless card sets were produced and distributed in the last month of 1941, you would almost have to say pre-war is anything before 1942.