Siege-train

A siege engine is a device that is designed to break or circumvent city walls and other fortifications in siege warfare. Some are immobile, constructed in place to attack enemy fortifications from a distance, while others are wheeled to enable advancing up to the enemy fortification. There are many distinct types, such as siege towers to allow friendly soldiers to scale walls, battering rams to break walls or gates, to catapults, ballistae, trebuchets and other similar constructions used to attack from a distance; some complex siege engines were combinations of these types.

Siege engines are fairly large constructions -- from the size of a small house to a large building. From antiquity up to the development of gunpowder, they were made largely of wood, using rope or leather to help bind them, possibly with few pieces of metal at key stress points. They could launch simple projectiles using natural materials to build up force by tension, torsion, or, in the case of trebuchets, manpower or counterweights coupled with mechanical advantage. With the development of gunpowder and improved metallurgy, bombards and later heavy artillery became the primary siege engines.

Collectively, siege engines or artillery together with the necessary soldiers, ammunition, and transport vehicles to conduct a siege are referred to as a siege-train.

The earliest engine was the battering ram, developed by the Assyrians, followed by the catapult in ancient Greece. The Spartans used battering rams in the Siege of Plataea in 429 BC, but it seems that the Greeks limited their use of siege engines to assault ladders, though Peloponnesian forces used something resembling flamethrowers.

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Wikipedia