page_title: Sloped armour
section_title: Historical application
hierarchical_section_title: Sloped armour / Historical application
caption_attribution_description: A Jagdpanther at the Panzermuseum Thun, Switzerland
context_page_description: Sloped armour is armour that is neither in a vertical nor a horizontal position. Such "angled" armour is often mounted on tanks and other armoured fighting vehicles, as well as naval vessels such as battleships and cruisers. Sloping an armour plate makes it harder to penetrate for antitank-weapons, such as armour-piercing shells and rockets, if they take a more or less horizontal path to their target, as is often the case. The better protection is caused by three main effects.
  Firstly, a projectile hitting a plate at an angle other than 90° has to move through a greater thickness of armour, compared to hitting the same plate at a right-angle. In the latter case only the plate thickness has to be pierced; increasing the armour slope improves, for a given plate thickness, the armour's level of protection at the point of impact by increasing the thickness measured in the horizontal plane, the angle of attack of the projectile. The protection of an area, instead of just a single point, is indicated by the average horizontal thickness, which is identical to the area density: the relative armour mass used to protect that area.
context_section_description: One of the earliest documented instances of the concept of sloped armour is in the drawing of Leonardo da Vinci's fighting vehicle. Sloped armour was actually used on nineteenth century early Confederate ironclads, such as CSS Virginia, and partially implemented on the first French tank, the Schneider CA1 in the First World War, but the first tanks to be completely fitted with sloped armour were the French SOMUA S35 and other contemporary French tanks like the Renault R35, which had fully cast hulls and turrets. It was also used to a greater effect on the famous Soviet T-34 battle tank by the  Soviet tank design team of the Kharkov Locomotive Factory, led by Mikhail Koshkin. It was a technological response to the more effective anti-tank guns being put into service at this time.
  The T-34 had profound impact on German WWII tank design. Pre- or early war designs like the Panzer IV and Tiger differ clearly from post 1941 vehicles like for example the Panther, the Tiger II, the Jagdpanzer and the Hetzer, which all had sloped armour. This is especially evident because German tank armour was generally not cast but consisted of welded plates.
  Sloped armour became very much the fashion after World War II, its most pure expression being perhaps the British Chieftain.  
  However, the latest main battle tanks use perforated and composite armour, which attempts to deform and abrade a penetrator rather than deflecting it, as deflecting a long rod penetrator is difficult.  These tanks have a more blocky appearance. Examples include the Leopard 2 and M1 Abrams. An exception is the Israeli Merkava.
caption: German designs from late World War II with well-sloped armour: the Jagdpanther tank destroyer and German Tiger II heavy tank in the background.
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