"Even with siege equipment, how can they possibly hope to reach us?"
The army brought along minimal siege equipment; they had the gifted to use as weapons of that sort.
However, the game has been upgraded with simple mounting options, or at least some sense of siege equipment.
A wide range of siege equipment was also used during the Second Empire.
Most importantly Manuel's siege equipment had been captured and destroyed.
A heavy army with siege equipment could not reach them through the wilderness.
The fire spread quickly, engulfing both towers and other siege equipment that had been brought up.
Additionally, a large army would have been able to force a crossing of the limes using siege equipment.
With them, they brought 500 cannons and other heavy siege equipment.
First, conventional siege equipment is less effective against a wall with a talus.