Siege tower

A siege tower, sometimes called a breaching tower or a belfry, is a specialized siege engine.

Its primary purpose was to protect soldiers as they approached the high defensive walls of a fortification. These massive structures were typically rectangular and stood on four wheels. To be effective, the tower's height often matched or exceeded the height of the enemy walls. This allowed archers or crossbowmen to stand on the top levels. From there, they could fire arrows and quarrels down into the fortification.

The mechanics of a siege tower required careful engineering and planning. Because they were so unwieldy, most towers were constructed on-site during a siege. They were used when other methods, like ladder assaults or battering rams, failed to work. Once the tower rolled close to a wall, it would drop a gangplank. This gangplank acted as a bridge for troops to rush onto the walls. Some towers also housed battering rams to bash through gates or stone walls. To protect the wooden structure from fire, builders used non-flammable coverings like iron or fresh animal skins.

History shows that these engines have been used for thousands of years. Evidence from the Bronze Age suggests they were used in Ancient Egypt and Anatolia.

In the 9th century BC, the Neo-Assyrian Empire used them under leader Ashurnasirpal II. During the 8th century BC, Kushite armies used towers to help their archers and slingers during the siege of Memphis. Even in ancient China, written records from the Han dynasty discuss different types of naval warfare involving towers.

Some siege towers were incredibly large and complex. The Hellenistic Greek engine known as the Helepolis was built during the siege of Rhodes in 305 BC.

Its name means "The Taker of Cities" in Greek. This machine was as high and wide as 40 meters. It had nine stories and was manned by 200 soldiers. Different levels of the Helepolis housed various catapults and ballistae. Moving such a massive weight required a rack and pinion system to move it effectively.

Despite their power, siege towers had specific weaknesses. They required very level ground to function correctly. If the terrain was uneven, the towers could not move. Defenders sometimes flooded the ground to create a moat, which would bog the tower down in mud. For hill-top towns, attackers sometimes built siege-mounds out of earth and rubble to create a level path.

The Romans used such a ramp during the siege of Masada between 72 and 73 AD.

During the medieval period, siege towers reached a new peak of complexity. At the siege of Kenilworth in 1266, a single tower operated 200 archers and 11 catapults. However, these towers were not invincible. During the Fall of Constantinople in 1453, Ottoman siege towers were targeted with Greek fire. Eventually, the development of large cannons made siege towers obsolete. Cannons could destroy walls more easily, which changed how fortifications were built entirely. In the gunpowder age, "battery towers" emerged to mount siege artillery instead of troops.

While the massive wooden towers of the past are gone, the concept lives on in modern technology. Today, some police tactical units and special forces use vehicles with mechanical assault ladders.

These ladders allow teams to reach the upper floors of a building to conduct raids. While they are much smaller than the Helepolis, they serve a similar purpose of providing access to high, defended points. They represent a modern evolution of the ancient idea of the mobile siege engine.