World War I was in full swing by 1915, when this drink was first sipped at the New York Bar in Paris. Much of France was a battleground, dotted with fearsome French artillery units, rolling their awe-inspiring 75mm field guns. This drink was named that year for that very gun, which may well have saved France and all the Allied powers from grievous defeat. We’ll drink to that!
Most versions of this drink have it with gin, but you’ve got plenty of historical support if you choose to use cognac or brandy instead. The amount of simple syrup you use depends on the sweetness of the sparkling wine (ideally Champagne) you use; we’re assuming a pretty dry variety, and so we use about a teaspoon, maybe less. Make sure that it’s quite chilled, whatever you use.
Build in the order given in a glass, and stir to mix.