Visual News has some very rare photographs taken during WWII. But they're in colour. There's also a larger selection which can be found at the US Library of Congress, but it's pretty daunting to browse.
When viewing really old photos, we're usually reminded of their age by the poor quality and lack of colour. These photos look strangely modern; as if taken with Instagram, today. This modern feel injects new emotion into the images, which is a strange sensation considering the era in which they were taken.