Roman siege machine, historical artwork. Telescoping tower raised from beneath by a screw mechanism, manipulated by two men. This would be used during siege warfare by the attackers, who would be able to winch themselves up at the wall or fortress in order to initiate an attack. This illustration was published in De Re Militari in 1532. De Re Militari was written around 390AD by Vegetius Renatus Flavius as a treatise of late Roman warfare, but it went on to become a military guide in the middle ages.