Bastion
Self-contained unit(s) of fortification projecting beyond the main curtain wall of a fortified place. Artillery, such as cannons, would be contained and infantrymen who could fire along the line of the curtain wall, so as to prevent the advance and scaling of the walls by an enemy.
Bastions would cover each other to prevent their direct attack by an enemy. Examples can be seen at Berwick upon Tweed (Northumberland) of the 18th century, though the principles had been developed in the 16th century.
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