Optimal treatment of pleural empyema remains controversial to the present day. In the preantibiotic era, surgical thinking favored early and aggressive drainage of closed-space infections, but the dynamics of the pleural space were poorly understood and open pneumothorax generally was considered the necessary price of surgical drainage. Against bitter opposition, revision of the dogma of early open drainage was achieved in 1918 by Evarts Graham and his associates on the US Army's Empyema Commission. Unacceptable mortality rates for early drainage were brought under control through a treatment program of repeated tapping, with surgical drainage only after loculation had occurred. Paradoxically, closed water-seal drainage for empyema had been used by a German internist, Gotthard Bülau, as early as 1875. His technique was published in 1891, 27 years before the report of the Empyema Commission. As a closed system, it would have been suited to empyema drainage in either the early diffuse or the loculated stages. Thoracotomy was not possible at the time, and Bülau probably could not foresee the future importance of his method to surgery.