Took me a while to get this when I read in the local paper, as they always cut off the first line. I thought somehow he was talking about the present war. Then I realised that today is Dec. 7.
Most comic strips have a logo box and a “throwaway panel,” which doesn’t need to be seen to get the strip. Newspapers don’t have to publish these to save space, and instead just run the name of the strip and its artist above the strip. Sometimes the throwaway panels represent something happening before the action of the rest of the strip, and in other cases they are another gag (in the case of this BC).
It does seem hard to understand without the throwaway panel, but remember what Franklin Roosevelt said about this date.
(Bill Watterson elaborates on strip space and throwaway panels in The Calvin and Hobbes Tenth Anniversary Book.)