Why walls were so hard to beat
For most of antiquity a walled city was a formidable obstacle. Thick mudbrick or stone walls, towers, gates and a water supply could allow a small garrison to hold out against a much larger army. Attackers therefore had four basic options: starve the city out, find a way over the wall, break through it, or go under it. Treachery and negotiation were also common, and many sieges ended without any assault. The machines and techniques below were the answers to the physical problem of the wall.
Assyrian assaults
The Assyrians are the earliest army for which we have a detailed visual record of siege technique. The carved wall panels from the palace of Sennacherib at Nineveh depict the capture of the Judaean city of Lachish, probably in 701 BCE, and these reliefs are among the best-known examples of Assyrian palace reliefs. They show an earth ramp piled against the walls, siege engines pushed up it, archers and slingers providing covering fire, and defenders hurling torches and stones from the battlements.
The engines in the reliefs are wheeled, covered vehicles with a battering ram projecting from the front. The ram was a heavy beam with a metal tip, and the cover, probably made of wood and wet hides, protected the crew from fire and missiles. The Assyrian reliefs also show soldiers undermining walls and using ladders. The Assyrian Empire was clearly skilled at combining these methods, and fear of its sieges was part of its political power, though its royal inscriptions naturally stress its successes.
Rams, towers and ramps
The core techniques were similar across many cultures:
- Battering rams struck at a gate or the base of a wall. Early rams were probably carried or swung by hand; later versions were hung from a frame inside a protective shed and could be rolled forward.
- Siege towers were mobile wooden towers taller than the walls, from which archers or boarding parties could fight at close range. They were covered with hides or metal plates against fire.
- Siege ramps and mounds were earth or timber embankments built up to the wall so towers and rams could reach it, or so troops could walk over. This was slow and dangerous work.
- Scaling ladders allowed a surprise assault, often combined with a diversion elsewhere.
- Artillery such as stone-throwers and bolt-shooters, which appeared in the Greek world in the fourth century BCE, cleared defenders from the walls.
At Tyre in 332 BCE, Alexander the Great’s engineers reportedly built a causeway across the water to the island city, an enormous undertaking, and the city fell after several months. Eventually the Macedonians combined the causeway with ships carrying siege equipment. A little later, Demetrius, nicknamed Poliorcetes (“besieger”), built a huge siege tower called the helepolis for his attack on Rhodes in 305 to 304 BCE. The Rhodians held out and the siege was abandoned, a reminder that giant engines were not decisive on their own.
Mining and counter-mining
Mining meant digging a tunnel beneath a wall or tower. The tunnellers propped the roof with timber, then set fire to the props so the wall above collapsed. Defenders countered by digging their own tunnels to meet the attackers, listening for sounds of digging, and sometimes flooding or smoking out the miners.
Some of the best archaeological evidence comes from Dura-Europos, a Roman garrison city on the Euphrates. When the Sasanian army attacked it, probably in the mid-250s CE, excavators found mines and countermines near the walls, along with the remains of soldiers who died in the tunnels. Interpretations of exactly what happened there are debated, but the site is a rare physical record of siege mining.
Roman methods
The Romans inherited Greek and Hellenistic techniques and made them routine. Roman commanders used ramps, rams, towers and artillery, but they also relied on extensive field engineering. At Alesia in Gaul in 52 BCE, Julius Caesar’s army built lines of fortification around the town and a second line facing outward against a relief army, a feat described in Caesar’s own account, which naturally presents it favourably.
The final siege of Masada in Judaea, around 73 or 74 CE, is another famous case. The Romans surrounded the rock with a wall and camps, then built a large earth ramp against the western side. The remains of the ramp and camps survive, and Josephus gives the surviving written account. Earlier, at the end of the Punic Wars, the siege of Carthage in 146 BCE led to the city’s destruction, a campaign that involved a blockade of the harbour and a long fight through the streets.
Roman legions also had permanent engineering skills, including bridge builders and artillery crews, which meant they could improvise siegeworks wherever they were. The camp-building practices covered in the account of Roman marching camps supported this.
How defenders replied
Besieged cities were not helpless. Defenders could:
- Build walls with towers that allowed flanking fire on attackers at the base.
- Dig ditches, so that rams and towers could not be brought close.
- Drop stones, fire and boiling substances, or swing hooks and beams to catch or break rams.
- Cover walls with hides and keep water ready to put out fires.
- Make sorties to burn machines.
- Dig countermines.
Over time, fortification design adapted to artillery and mining, with thicker walls, projecting towers and outworks. The contest between attack and defence continued through the whole period.
Reading the evidence
Details of siege engines come from a mix of reliefs, treatises such as those on artillery by Greek and Roman engineers, and accounts by historians who were not always eyewitnesses. Numbers of men, sizes of engines and the length of sieges are often unreliable. Archaeology gives a firmer base where ramps, tunnels and projectile heads survive, and these remain the best check on what the texts claim.