The Roman legion on the move was not just a fighting force it was a mobile city, with a baggage train (impedimenta) that carried everything needed to sustain and deploy it. Siege engines ballistae, onagers, and scorpiones were essential for both offense and defense, but they were not built on the spot. The Romans relied on prefabricated parts: torsion springs, wooden frames, iron fittings, winches, and tools, all transported in wagons or on mule back. These components allowed for rapid assembly, a hallmark of Roman military efficiency.   
  
Illustrations by Peter Connolly and Enrico Marini depict how the baggage train included specialized carts and mules carrying disassembled artillery.  Each legion, under the early Empire, was expected to maintain a standardized artillery train fifty-five scorpiones and ten onagri, as Vegetius notes.  These were not makeshift weapons. They were mass produced in imperial fabricae (workshops), ensuring uniformity and ease of repair.   
  
While some field construction occurred especially during sieges like Jerusalem in 70 AD. this was the exception. The norm was modular design and logistical foresight.  Caesar’s forces at Alesia used prefabricated towers and artillery, proving that speed and preparation trumped improvisation. The fabri, skilled engineers and craftsmen, oversaw assembly, ensuring that siege engines were combat-ready within hours.   
  
The baggage train was not just about siege engines. It carried food, tents, tools, and medical supplies. But the presence of artillery components underscores a key truth: Roman power was not just in the sword, but in the logistics that made it possible.   
  
SOURCE:  
  
Grokipedia – Roman Siege Engines  
[https://grokipedia.com/page/Roman\_siege\_engines](https://grokipedia.com/page/Roman_siege_engines)  
On prefabrication, modular design, and logistical transport of siege equipment.   
  
LacusCurtius – Trajan’s Column: Artillery and Siege Trains  
[https://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/Europe/Italy/Lazio/Roma/Rome/Trajans\_Column/John\_Pollen/Artillery\*.html](https://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/Europe/Italy/Lazio/Roma/Rome/Trajans_Column/John_Pollen/Artillery*.html)  
Primary source analysis of artillery depictions on Trajan’s Column and Vegetius’ account of legionary artillery.   
  
Karwansaray Publishers – March: Noncombatants and Legion Baggage  
[https://www.karwansaraypublishers.com/en-us/blogs/gary-brueggemans-the-roman-army-ancient-warfare/march-noncombatants-and-legion-baggage](https://www.karwansaraypublishers.com/en-us/blogs/gary-brueggemans-the-roman-army-ancient-warfare/march-noncombatants-and-legion-baggage)  
Detailed breakdown of baggage train composition, including artillery transport and mule loads. 

AGMEN - Roman legion on the move marched in a formation