The bastion was the main feature of the new defensive design known as the bastion system or Fronte Bastionato. This was first implemented in the 16^th century and completed in the 17^th, to afford better protection from new firearms created after the invention of gunpowder.

Bastions are large, solid constructions projecting from the main line of defence, designed to protect adjacent bastions, the curtain wall and the ditch.