page_title: Glacis
section_title: Early modern European fortifications
hierarchical_section_title: Glacis / Early modern European fortifications
caption_attribution_description: Français&#160;: Glacis, fort militaire, Mont-Louis, Pyrénées-Orientales, France
context_page_description: A glacis in military engineering is an artificial slope as part of a medieval castle or in early modern fortresses. They may be constructed of earth as a temporary structure or of stone in more permanent structure.
  A glacis plate is the sloped front-most section of the hull of a tank or other armoured fighting vehicle.
  More generally, a glacis is any slope, natural or artificial, which fulfils the above requirements. The etymology of this French word suggests a slope made dangerous with ice, hence the relationship with glacier.
context_section_description: Early modern European fortresses were so constructed as to keep any potential assailant under the fire of the defenders until the last possible moment. On natural, level ground, troops attacking any high work have a degree of shelter from its fire when close up to it; the glacis consists of a slope with a low grade inclined towards the top of the wall. This gave defenders a direct line of sight into the assaulting force, allowing them to efficiently sweep the field with fire from the parapet. Additionally, but secondarily, the bank of earth would shield the walls from being hit directly by cannon fire.
  Though defenders on a high ground already have a direct line of sight, a glacis allows the field of fire to be swept more efficiently by minimizing changes to the angle of their guns while firing.  Furthermore, the glacis prevents attacking cannon from having a clear shot at the walls of a fortress, as usually these cannot be seen until the glacis is crossed and the ditch, bounded on either side by the smooth, masoned scarp and counterscarp, is reached.
caption: Glacis, Mont-Louis Fortress, Pyrénées-Orientales, France
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