How was beer production affected by the war during WW2?

Question

How did the war affect beer production during World War II? This is a follow-up question to this question at Seasoned Advice, which is gathering interesting food-science answers but which are are short on historical perspective and long on historical speculation.

This source cites various brewer's almanacs for evidence that beer strength suffered during WW2, but doesn't indicate why. Of course there were supply issues, but what and why (and what substitutions might have been made) are the interesting details that would help support or discredit the answers the original Seasoned Advice question is getting. And besides supply, there could have been political, social, or rationing pressures on how beer was produced and distributed.

So speculation aside, how did the war affect beer? Lingering after-effects of the war might be interesting, but that's not the main point of this question.

Answer 1

http://www.oldbeers.com <- contacting the owners of the Pretty Things Brewery might be able to help. They have a project brewing old beer recipes.

Basing my answer off a single source (the 1945 beer recipe used by Pretty Things) it appears that there was limited variety in brewing materials as well as a lower alcohol content. It makes sense, as you can't limit the amount of beer, but you can use fewer ingredients to make the beer while rationing.