As with beards, sideburns went quickly out of fashion in the early twentieth century, and in the First World War in order to secure a seal on a gas mask, men had to be clean-shaven; this did not affect mustaches.
Men had to be clean-shaven. Sideburns went quickly out of fashion in the early twentieth century, and in the First World War. This was with beards. This was to secure a seal on a gas mask. This did not affect mustaches.