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The Cz-91 (Czołg 91) or Pasaras 21 is a main battle tank developed by Bloodia and Kus. Variants continue to serve as the primary battle tank of Bloodia and Kus. It has received multiple upgrades and is an important asset of both nations military services.

Development
Development of Czołg 91/Pasaras 21 began in the early 1980s in an effort to unify Kusian tank force to use a single vehicle and correct issue stemming from the Bloodian Cz-64/71/76 concept, combining both elemets and concepts of Kusian and Bloodian   and  that were in Bloodian and Kusian service at that time. Designers began drafting plans to improve upon the the Cz-76 design to provide more protection for the crew, an improved autoloader and blowout panels. The new project was dubbed Project 1488, brining its first prototype in 1989.

Production history
The Cz-91 was approved for mass production by the Directorate of Defense in 1990 with the intent in replacing the Cz-71 tank fleet. The export variant without blowout panels was approved in 1994.

Service History
The Cz-91 first entered service in 1991, and has since become the primary MBT beginning to replace frontline Cz-71's to work alongside the Cz-76 in 1995. Many upgrades have been made since the original design first went into production, starting with the Cz-91-2 with updated ERA and an APS system and ending with the most recent iteration with the Cz-91-3 with new sideskirt ERA, a new 14x100mm autocannon, better thermals and the new B-135-117 135mm smoothbore gun.

Combat history
The Cz-91 first saw combat in the Second Nayili War mostly fighting against inferior Cz-71, Cz-58 and GSČ-65, although not much tank on tank combat was seen, in the tank battles which it participated Bloodian officials claim the Cz-91 destroyed 300 armoured targets (including IFVs, APCs and MRAPs) while neutral observers claim that an estamiated 107 armoured targets were destroyed by the Cz-91 while the rest were destroyed by missile or air strike. Throughout the war only 3 Cz-91s were destroyed, 1 to friendly fire by air strike and 2 by scuttling, they were detracked in the desert and thus ordered to be destroyed by plastic explosive to prevent insurgent capture.

Armament
The Cz-91's main gun is the Bloodian B-125-90 125mm smoothbore tank gun. It is a modified gun from the Cz-80, it is capable of firing armour-piercing fin-stabilised discarding sabot (APFSDS), high-explosive anti-tank (HEAT-FS), and high explosive fragmentation (HE-FRAG) ammunition, as well as anti-tank guided missiles. This tank gun was later replaced in the Cz-91-3 models with the B-135-115 135mm smoothbore tank gun which is capable of firing armour-piercing fin-stabilised discarding sabot (APFSDS), high-explosive anti-tank (HEAT-FS), and high explosive fragmentation (HE-FRAG) ammunition, as well as anti-tank guided missiles.

Cz-91's secondary armament is fitted with either a 14x100mm machine gun or 20mm anti-air canon, depending on role within the ground forces) both of which are remotely controlled inside the tank and has a 7mm coaxial machine gun. The tank is fitted with an autoloader for the tank gun.

Mobility
Fitted with the Kusian designed engine, it allows the Cz-91 to maintain a high speed with decent fuel consumption while also able to maintain a decent reverse speed.

Protection
The Cz-91 is fitted with a "three-tiered" protection system. The first tier is the composite armour in the turret, consisting of basic armour shell with an insert of alternating layers of aluminum and plastics and a controlled deformation section. The second tier is third generation ERA (explosive reactive armour) which significantly degrades the penetrating power of kinetic-energy APFSDS ammunition; these ERA blocks give the turret its distinctive angled "clam shell" appearance. ERA bricks are also located on the turret roof and provide protection from top-attack weapons. The turret's forward armour package, in addition to the ERA and steel plating. The composite armour results in a lower weight and improved protection when compared with steel-only armour. The third tier is the softkill and hardkill active protection systems, smoke dispenser and blowout panels.

Bloodian variants

 * Szczadzieta-1488: First prototype demonstrated in 1989
 * Cz-91: First iteration with blowout panels, new autoloader and 125mm smoothbore gun
 * Cz-91W: Developed as an export variant for the Cz-91 (no blowout panels and reduced electronics)
 * Cz-91-2: Second iteration of the Cz-91, developed in 2001 with upgraded ERA
 * Cz-91-2W: Developed as an export variant including the blowout panels but reduced electronics
 * Cz-91-3: Third iteration of the Cz-91, developed in 2016 with upgraded ERA, upgraded blowout panels, upgraded optics, new thermal sights, upgraded comms, upgraded electronics, upgraded APS system and new 135mm smoothbore gun along with a new autoloader for the new gun system.

Operators

 * Bloodia
 * People's Commonwealth Land Forces– The Bloodian National Land Forces operate about x Cz-91, x Cz-91-2 and x Cz-91-3.