How prevalent were tea bags during WW2 ?
In the movie
Stalag 17, the prisoners had a used tea bag that they kept using.
A movie as a source of history? Tsk, tsk.
I suspect the use of teabags came about (in POW camps) because they were convenient to use, not because they tasted well. And, in a prison camp, or a POW camp, ingenious solutions to everyday problems are usual, because needs must, and needs give rise to unorthodox and often every clever solutions.
I don't know whether POWs used teabags during WW2; firstly, it wouldn't surprise me, secondly, I would never use a movie as a source of historical knowledge, and thirdly, I'd bet my savings on the fact that when those chaps returned home, or were repatriated after the war, they most certainly didn't use teabags. In those days, tea mattered, and good tea was recognised.
In any case, my grandparents - on both sides - never used tea bags; family lore suggests that one grandfather, on my mother's side, who worked in the agriculture ministry and was a shrewd, prudent man, concluding, (correctly) that war was coming, and recognising that rationing would be an inevitable consequence of this, managed to procure a tea chest (of tea) shortly before the war which had the effect of ensuring that his family were well supplied with tea for much of the duration.
Neither did my uncles and aunts (use teabags), nor the parents of my friends.
Instant coffee (ugh) yes, but teabags never; they were considered an affront to good taste, if highly convenient.
When I was a child, we didn't either, we used a teapot, and a strainer; indeed, I don't recall seeing teabags used until I became a student, and my mother had a promotion at work which meant that she became a lot busier, and time mattered more; this was the 80s, a mere 40 years after world war two.