This is the title of an article in the latest Kelleher's Stamp Collector's Quarterly, vol 6, #3. If you aren't familiar, the magazine features consistently well written and consistently well illustrated articles. I can imagine non-collectors paging through one in a doctor's waiting room.
The premise of the article is easily discernible from the title, although not so obvious might be the collectors of the era who wanted nothing to do with "enemy" stamps.
But I bring the article up as a reminder that we partly owe WWI for the Junior International which, of course, become the Big Blue. Here is an ad for the Junior (first issued in 1914) that I posted on this blog in 2008.
In case the scan isn't clear:
"When you are Daddy's age you will be telling your children all about the great war of 1914 that changed the map of Europe. You will want to show them the splendid collection of stamps you made of all the countries now at war, and tell them about Belgium and Russia and France and Germany. And you will be very proud of your collection, too, because, 'way back in 1914, when you realized how interesting these stamps would be some day, you arranged them neatly, as shown above, in your new JUNIOR INTERNATIONAL ALBUM."
You can peruse the entire issue at this link. The article is on page 34.