I've seen numerous articles claiming that WWII affected the beer bottling industry which caused a change (reversion) from it being sold in brown glass bottles to green.
Sometimes the articles, such as here, say that brown glass was needed during the war which caused the shift. Sometimes, such as here, the claim is that after the war there was a shortage of brown glass and that is when the change was made.
My question first of all is which of these is true? Was the change made during or after the war?
Second of all, unassuming the change was made during the war, why would brown glass be needed during the war leaving the private industry with only green? And on the flip side, if the change was made post war, why was there only a shortage of brown glass?