History of Siege Towers

Siege towers are some of the largest and most advanced medieval weapons ever conceived. The main purpose of a siege tower is to attempt to provide assaulting soldiers access over castles battlements, city walls or any other high fortifications obstructing access to the enemy. They were very large structures and needed to be pushed to the base of the fortification. This made siege towers a huge and critical target for the enemy.

Generally siege towers were only used as a last resort. If it was not possible to breach fortifications with lesser methods the siege tower would be used. Other methods included;

• Ladder assault (escalade): Soldiers would scale the wall via means of a ladder to climb over the fortification. This was often conducted under fire from the enemy; this method was easy to counter.
• Mining: While under fire soldiers would dig or tunnel under enemy fortifications.
• Breaking walls or gate. Attackers would attempt to smash their way past defences to gain access to the enemy.

The above methods were less involved than using a siege tower but at times were not possible. If any of these methods were unsuccessful or could not be conducted the soldiers would need construct a siege tower.

Because of its weight and size, siege towers were created on the site of the siege. They were either constructed from easily accessible materials or were built prior to the siege and reassembled on site. Normally a siege tower was constructed from wood which meant they were venerable to fire; it was often covered with metal armour or animal skin (leather) to provide protection. A siege towers was built as high as the fortification or slightly higher so that archers could be mounted on top of the tower providing covering fire. The front and side of the tower were sealed/covered so that the contained soldiers were protected from enemy fire. It was normally rectangular in shape and was mounted on wheels.

The objective of using a siege tower was to push the tower up against or near the wall or fortification being assaulted. At which point the attackers would drop a gangplank on to the fortification which acted as a bridge between the fortification and tower. The gangplank also opened up the siege tower letting the attackers exit the tower via the gap it previously covered. Siege towers sometime housed other larger military projectile weaponry used to assault the enemy while the tower slowly moved towards its target.

In order to defend against siege towers many defenders opted for the use of water. Area around the fortification was flooded causing the earth to become muddy or unstable. This meant that the soil was not fit to support the weight of the siege tower. Moats were also built around fortifications disabling a siege towers access. Through the medieval period of siege towers, attacker would make use of ‘Sows’ (mobile fortified shelters) and fill in moats or muddy soil to make the ground level and stable for the siege tower to perform its function. Some fortifications that needed assaulting were built on hills or in other topographic advantageous positions; this made the use of siege towers difficult or impossible. Attackers would use Sows to help build ramps that would allow siege towers access to the base of the fortification. Other siege towers were mounted on ships used to assault areas of fortifications that were on waters edges. Built on later medieval fortification were ‘talus’. A talus was used to deter typical methods of siege including siege towers. A talus was a sloped wall placed in front of a fortification. This provided the following advantages;

• Ladders used to breach the fortification needed to be longer in order the make up for the extra horizontal distance caused by the talus. This also put much stress on the ladder increasing the chance of it breaking or being destroyed.
• The gangplank of the siege tower had to be much longer in order to cover the distance. This rendered many of them useless. If the gangplank was long enough it increased the distance between the tower and fortification. Making it harder for attackers to breach the wall as they hard further to travel over the gangplank.
• Defenders could hurl large projectile from the top of the fortification down on to the talus. This would break apart on impact and shower the attackers at the base of the talus in shrapnel.

A Talus would make it difficult to use typical methods of seige

Eventually siege towers started to vanish with the introduction of gun powder and the invention of large cannons. The only job of a siege tower was to breach an enemy’s high fortifications. These fortifications were no longer an effective defensive against cannon weaponry; hence other methods of fortifications were conceived and siege towers become a thing of the past.