" Born of the Great War, this “trench broom” meant to help American doughboys sweep their way across Europe. But the conflict ended too soon for the Thompson to take part, and many of the fifteen thousand guns in circulation by 1929 ended up in private hands. Because the weapon was so new, few laws governed its sale. Legally purchasing a tommy gun in Chicago, in those days, was easier than acquiring a handgun. "

― Max Allan Collins , Scarface and the Untouchable: Al Capone, Eliot Ness, and the Battle for Chicago