... But ikey, BryanJ didn't say anything about World War Two! ??? ...
Yes, erilaz, but what he did
... I have been collecting Militaria items for years ...
... which sounds like a pretty generic interest, in which case WW1 is far more, well, target-rich environment for postcards than WW2.
Not to mention the quality
. Many/most of the US military-theme cards were white-border-era cards with terrible color registration - the darned things can be painful to look at, regardless of subject - while WW1 cards included an ocean of real photo small unit group portraits, "I have arrived safely" AEF cards, BDA (Bomb Damage Assessment) cards, etc.
There was a reason that they called it The Golden Age.