A Cage Won’t Save You

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Cope cages are slat armor mounted above a tank’s turret. They appeared on Russian tanks in 2021, before the Russian invasion of Ukraine in 2022. The term “cope cage” was coined during the early days of the invasion when Russian tanks with this armor mounted were still being destroyed by anti-tank guided missiles (ATGMs), particularly top attack missiles like the NLAW and Javelin.

The Javelin has a contact fuze which seems to function just fine when striking slat armor and thus both tandem charges are still fired. The distance between the slat armor and the base armor is less than optimal for the Javelin which is supposed to detonate right on the main armor or on an ERA block, but since the Russian turret top armor is so thin, the Javelin can still perforate the roof and kill the tank. The NLAW uses a proximity fuse, so unless it faceplants into the cage, which requires the cage to be at just the right height, the missile will still detect the tank underneath and fire its warhead.

It turns out that while cope armor is useless against most Western munitions, it’s a good defense against Russian anti-tank rounds. It can be effective against cheaper projectiles like the ubiquitous PG-7V launched by the RPG-7. These fuses aren’t effective unless they strike a continuous surface.

In the image above, the PG-7V fails to fuse properly against slat armor. The reason for this is that the metal slats slice into the front of the rocket before the electrical signal can be properly sent to the warhead from the contact fuse, which is placed on the tip of the nose as shown in the diagram above. If the fuse hits one of the slats directly, the warhead will still be triggered, but since most of the surface area covered by the slats is open air, it’s more likely than not that the fuse won’t hit the slat.

More sophisticated fuses can reliably trigger the warhead regardless of what portion of the projectile’s front strikes a target, and these aren’t as vulnerable to slat armor.

The issue with top-mounted slat armor/Cope Cages is that incoming projectiles from above are much more likely to use either a more sophisticated contact fuse or a proximity fuse. Thus, they are of minimal effectiveness against things like top-attack missiles and anti-tank cluster munitions, such as DPICM recently provided to Ukraine and the sensor-fused weapon that can be carried on the F-16 that will be delivered to Ukraine.

Cope Cages (top-mounted slat armor) isn’t entirely useless. In urban terrain, Cope Cages can save a tank from a Russian RPG fired from a rooftop. In addition, loitering munitions don’t often have the best fuzes.

In addition, since loitering munitions often have long wins and wings, it’s possible that a drone coming in at a shallow angle will have its fins strike the slats before the warhead detonates, which could cause the drone to be torn apart by the impact and rendered harmless. (above)

While Russia lacks top shoulder-fired top-attack missiles, it has plenty of Lancet drones, which explains why many Ukrainian vehicles, including their Challenger 2 tanks, are now also fitted with Cope Cages/slat armor that protects the top of their turrets.



The Mot and Bailey (a cage might save you)

This is a digital reconstruction of a small fortified residence of a member of the low nobility. (a diorama made by Karel Lhotsky) Possibly a poor knight or shire reeve would occupy a residence such as this one. Frequently they’d be built on a stream or river so that a water wheel mill (income-producing) could be installed within or adjacent to the walls. Even though you might think that a fortification such as this one could be easily breached, it took considerable force (or guile) to do so. There were many more mot and bailey forts than stone castles for obvious reasons. Most of them were larger than the above depicted.

In the Middle Ages knights owed fielty to their liege lord – a baron or an earl. This translated to an agreed-upon number of days of service. The knight could provide himself and five equipped men at arms for thirty days, for example, or he could buy the service of an equivalent force to meet that obligation.

Knights were granted tracts of land and peasants were indentured to that land. There were rules about how many days they had to work for the local knight, and how many days they could work for themselves. Sometimes there were stone quarries or small ports attached to the landhold. Sometimes there were villages and if they wanted to hold a market, they had to receive a Royal charter to do that with proceeds distributed up and down the feudal chain.

Knights fought in mock battles (later called tournaments) wherein they could lose a horse, saddle, armor, weapons, etc. if they fought poorly. Wagering stood at the heart of these war games. It was good practice with consequences for poor performance.


14 thoughts on “A Cage Won’t Save You

  1. A Motte and Bailey looks, as you said, less than ideal for defense. But… The steep walls of the motte or moat stopped cavalry and made infantry assaults quite difficult. Most people wouldn’t believe how much difference even 1 foot of height difference makes in hand-to-hand combat, but it does. And to do that on a serious slope really really sucks. Bonus is building the mound and interior of the walled compound out of the spoils from the moat.

    The wall usually starts as a wooden palisade, but over time would be replaced by stones and rocks from the fields as the supply is available.

    And the height of the donjon or keep makes it quite useful for firing missiles from and for command and control.

    Little known fact: William the Conqueror carried pre-built wooden keeps with him as he crossed the Channel and set them up whenever he stopped for a reasonable break.

    1. The peasants were required by law to spend time practicing at the butts with yew bows so the knight had archers at hand as well. The fyrd morphed into longbowmen who could do a lot of damage to attackers

      1. Except in France, where the nobility was scared poopless over peasants having long-distance weaponry. But that’s France.

      1. The style of structures varied but construction was usually designed for the protection of the animals on the first level so it tended to be open. There are thousands of these structures still standing in England. Built on the foundational level they tended to use ‘daub and wattle’ because it was light, strong, and provided insulation. A woven lattice of wooden strips called wattle was daubed with a sticky material usually made of some combination of wet soil, clay, sand, animal dung, and straw.

        Sieges in England and in Europe (usually civil wars) rarely included the use of (Roman-style stone-throwing) artillery or siege engines, so taking fortifications meant storming the ramparts. Thud daub and wattle worked for many structures. It was inexpensive and functional.

        1. Also a good demonstration of just how horribly poor even the rich people were in the Olden Days.


  2. As to COPE cages, if it’s stupid but works, it isn’t stupid. Like sandbags and wooden logs on the sides of tanks in WWII to pre-detonate HEAT warheads.

      1. The Army didn’t remember ’em, or anyway, how to do it. According to my buddy in Army transportation corps, or whatever they call it now, when they started doing all those road convoys in Iraq, they had to root around in the archives and look for old people down at the VFW who remembered how to do it. Some stuff on Yoot-tube about it.

        As to RPG’s, you look at pics of mech units in Viet Nam, you’ll see rolls of cyclone fencing tied on top of the tracks, to be put out when they set-in at night.

      1. I would lay claim if I had to construct it, including all that excavation for moats and what appear to be ramparts. Animals below, living quarters above with a decent view of surroundings. Not a center hall Colonial, but certainly has its charm.

  3. The Cope Cages are also effective against the HEAT rounds for the Vasilek mortars and the Nona / Vena 120s. Also Western guided mortar rounds like Strix et al.

    Besides, it’s cheap and it might make the tankers feel a little better.


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