I was reading the following article:

http://www.slate.com/blogs/the_vault/2017/08/04/a_cookbook_published_by_american_women_during_the_berlin_blockade.html

and one of the recipes includes the use of soy sauce. This cookbook is intended for usage under siege conditions, where exotic or unusual ingredients would probably be very hard to get ahold of. Soy sauce would then, I assume, be a very common thing in a German kitchen.

Does anyone know how far back this would have been true?