Well, the Wahl electric hair clipper was patented in 1921, and was the first electric hair clipper.

Prior to that, it would have been a classic straight razor shave with either oil or soap/foam.

If you mean BALD shaved, then there have always been a certain % of men doing that in most cultures.

If you mean "army buzzed" then it probably didn't get popular until after Wahl's invention took hold.