Fourth Regiment is an old cocktail that is essentially a variation on the classic Manhattan. It is prepared with a 1:1 ratio of vermouth and whiskey, with the addition of three different bitters – celery bitters, orange bitters, and Peychaud’s or Angostura bitters.
All ingredients are stirred with ice, then strained into a cocktail glass and garnished with a lemon twist. The origins of the cocktail are still unclear – some sources say it first appeared in a 1931 version of The Gentleman’s Companion, while others say it was first mentioned in 282 Mixed Drinks from the Private Records of a Bartender of the Olden Days from 1889.