The martini is a cocktail made with gin and vermouth, and garnished with an olive or a lemon twist. A dry martini is made with little to no vermouth. Ordering a martini "extra dry" will result in even less or no vermouth added. By the Roaring Twenties, it became a common drink order. Over the course of the 20th century, the amount of vermouth steadily dropped.
Add the gin, dry vermouth and orange bitters into a mixing glass with ice and stir until very cold.
Strain into a chilled cocktail glass.
Garnish with a lemon twist.