There are stories about men who joined the U.S. military in the late 20th Century who were allowed to drink earlier than they would have been allowed to in their home state. As states moved their drinking age up to 21, the military first chose to have a standard drinking age of 18 across all U.S. bases. The policy then changed to reflect the drinking age of the locality the base was in.

A retired Air Force officer jh tells us:

Yes, back when I first joined you could drink on military bases at age 18. The reasoning was they'd rather the guys get plastered on base where there was less of a chance to get in trouble and get a DUI. But then again back in those days there were still a few states which had their drinking ages at 18. For example when I got to my first duty station in South Carolina they had a law where you could buy beer at 18 but had to be 21 to buy liquor. Then the military adapted this policy...the drinking age on base or post would reflect whatever state/country law where the base was located. For example if you could be 19 and stationed on one base where the state's drinking age was 21 and you couldn't drink. But if you got orders or went TDY to another state where the age limit was 18, then you could drink again. Today I don't think any states have a limit below 21 but I could be wrong. One of my last assignments was Korea in 2001 and the drinking age in that country is 20 so people got to turn it on a year early when they were there.