The Siege Towers or Attack Towers were tall, towering, powerful and effective siege unit. It was a specialized siege engine constructed to protect assailants and ladders while approaching the defensive walls of a fortification. Because of its gargutuan size, it was moved by as much as four trolls. The siege engines was the fact that it could cary as much as 50 troops while protecting them from any enemy fire. The giant towers also were a great presence on and would strike fear into the enemies' hearts. The Siege Tower is notably used by the Enemy of the Free World, Mordor.
The Siege Tower had several notable uses. One of its uses is to carry/transport troops. With its many levels and floors, the Siege Tower could hold up to at least 50 troops. If enough Siege Towers that were filled to the brim, Mordor could deploy massive armies straight onto enemy walls. This would advantage them very much throughout any war as they could control the Fortress perfectly if the walls were captured early.
The Siege Tower was notably used by Mordor during the Third Age. Mordor, being highly advanced at that time in technology created the siege engine at a fortified ladder which could carry many more men and could not be pushed of the walls by enemy troops. Mordor used this siege engine in a number of famous battles, but very possible the most famous one was the Siege Of Minas Tirith.