page_title: Bastion fort
section_title: Construction
hierarchical_section_title: Bastion fort / Construction
caption_attribution_description: English: Geneva 1841Français&#160;: Plan de Genève en 1841
context_page_description: A bastion fort or trace italienne, is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-15th century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.
  The design of the fort is normally a polygon with bastions at the corners of the walls. These outcroppings eliminated protected blind spots, called "dead zones", and allowed fire along the curtain from positions protected from direct fire. Many bastion forts also feature cavaliers, which are raised secondary structures based entirely inside the primary structure.
context_section_description: Bastion forts were very expensive. Amsterdam's 22 bastions cost 11 million florins, and Siena in 1544 bankrupted itself to pay for its defences. For this reason, bastion forts were often improvised from earlier defences. Medieval curtain walls were torn down, and a ditch was dug in front of them. The earth used from the excavation was piled behind the walls to create a solid structure. While purpose-built fortifications would often have a brick fascia because of the material's ability to absorb the shock of artillery fire, many improvised defences cut costs by leaving this stage out and instead opting for more earth. Improvisation could also consist of lowering medieval round towers and infilling them with earth to strengthen the structures.
  It was also often necessary to widen and deepen the ditch outside the walls to create a more effective barrier to frontal assault and mining. Engineers from the 1520s were also building massive, gently sloping banks of earth called glacis in front of ditches so that the walls were almost totally hidden from horizontal artillery fire. The main benefit of the glaces was to deny enemy artillery the ability to fire point blank. The lower the angle of elevation, the higher the stopping power.
  The first key instance of a trace Italianate was at the Papal port of Civitavecchia, where the original walls were lowered and thickened because the stone tended to shatter under bombardment.
caption: Plan of Geneva in 1841. The colossal fortifications, among the most important in Europe, were demolished ten years later.
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