The artillery was used to most effect in sieges, where its role was to blast breaches in fortifications for the infantry to assault. Cromwell and the other commanders of the Army were not trained in siege warfare and generally tried to take fortified towns by storm rather than go through the complex and time-consuming process of building earthworks and trenches around it so that batteries of cannon could be brought close to the walls to pound it into surrender. The Army generally performed well when storming fortifications, for example at the siege of Drogheda, but paid a heavy price at Clonmel when Cromwell ordered them to attack a well-defended breach.