In the spring of 1861, with secession in full flower and Baltimore occupied by General Benjamin "Beast" Butler's nervous Union troops, reports emerged that southern sympathizers there possessed a terrible weapon of mass destruction, one capable of firing 300 rounds per minute and utterly destroying anything in its path. But not everyone was impressed. "A very amiable machine, indeed, for killing friend and foe," said the Scientific American. "We suppose the inventor intended to use it for the purpose of committing suicide." What was this awful "engine of war," and did it ever work? John Lamb presents for the first time in print the full story of the "Winans Steam Gun" and its antecedents, from inception in the fertile--sometimes fantastical--minds of nineteenth-century mechanical engineers, through personal jealousies, patent disputes, and test firings. Here too is the story of Ross Winans, the colorful, rabidly pro-Southern Baltimore industrialist to whom the gun was mistakenly attributed, and who was seized and briefly imprisoned after its capture.