Marcus Vitruvius Pollio (born c. 80–70 BC, ied after c. 15 BC) was a Roman writer, architect and engineer (possibly praefectus fabrum during military service or praefect architectus armamentarius of the apparitor status group), active in the 1st century BC. By his own description Vitruvius served as a Ballista (artilleryman), the third class of arms in the military offices. He likely served as chief of the ballista (senior officer of artillery) in charge of doctores ballistarum (artillery experts) and libratores who actually operated the machines.