One of the common rejoinders employed by battleship critics is that modern anti-ship missiles would quickly and easily sink a battleship. Of course, this statement is made with zero supporting evidence. On the contrary, there is much evidence that suggests – but does not explicitly prove – that battleships would be largely immune to anti-ship missiles.
Battleship critics have suggested two modes of ‘killing’ a battleship:
- Outright sinking using modern anti-ship cruise missiles
- Mission killing due to destruction of top side electronics, sensors, and weapons
We’ll examine each of those modes but, first, let’s understand some underlying concepts.
Armor Piercing Shells – A battleship’s main weapon was the 16”+ gun firing 2500 lb armor piercing (AP) or high explosive (HE/HC) shells travelling at velocities of Mach 2+. For example, the Iowa’s 16” AP/Mk8 weighed 2700 lb and had a muzzle velocity of 2425 ft/sec (1653 mph, Mach 2.1).
What is an armor piercing (AP) shell?
U.S. Navy World War II nomenclature uses the words "Armor Piercing" (AP) to mean that the base-fuzed, hard-nosed projectile so labeled has a thick, steel AP cap designed to allow intact penetration through some thickness of Class "A" (face-hardened) armor plate.
|AP Shell Mk 8|
Armor piercing shells were designed, as the name implies, to penetrate a ship’s armor. This was accomplished by placing a heavy, solid metal cap over the explosive shell. Grossly simplifying, the cap was a sacrificial ‘point’ that would penetrate the armor allowing the explosive shell behind it to enter the ship intact and functional before exploding.
Armor – A battleship’s armor (we’re talking about US battleships in this post) is intended to protect vital equipment. Any equipment not protected is not vital – useful, undoubtedly, but not vital. As a general statement, battleship armor was designed to provide immunity to another battleship’s weapons which means 16”+ shells. It is noteworthy that the Iowa class was designed to be immune to 16” plunging fire.
Armor was not, as so many people believe, simply thick plates of steel attached to the sides of the ship. Instead, it was a sophisticated system of plates, layers, carefully calculated void spaces, differing materials and treatments of steel, calculated angles (obliquity), etc. all working together to defeat attacking shells.
The main mechanism of armor protection was the act of decapping incoming AP shells before they could penetrate the armor. In other words, the armor was designed to strip the armor piercing cap off the incoming shell before penetration could occur. If the shell could be decapped, the shell’s penetration would be prevented or severely limited. Navweaps website has articles by Nathan Okun that go into much greater detail, for those interested.[1,2]
Armor penetration requires a rather lot of information, but decapping of the projectile by breaking the rather weak solder and/or mechanical bond between the nose and cap base is very, very simple:
0.08-0.08049-caliber thickness of any kind of homogeneous iron or steel plate has a 50% chance of decapping any kind of capped projectile over 40mm in diameter under ANY impact condition, penetrating or not.
0.0805-caliber and up thickness always decaps the projectile, penetrating or not.
The USN Iowa and South Dakota class battleships have an internal inclined main armor belt. What isn't well known is that they also have a shell plating outside of this belt that acts as a decapping plate. On the South Dakota's, this shell plating is 1.25" thick (3.2 cm) and on the Iowa's it is 1.5" thick (3.81 cm). Using Nathan's formula above, the South Dakota's plating would be sufficient to decap any projectile up to 15.5" (39.4 cm) and the Iowa's plating would be sufficient to decap any projectile up to 18.6" (47.3 cm). This would imply that the Japanese Type 91 18.1" (46 cm) APC projectiles fired by the Yamato would be decapped by the Iowa's shell plating before they reached the main armor belt. Decapping an AP projectile greatly decreases their armor-penetration ability against face-hardened naval armor (unprotected projectile nose now shatters into pieces) at under 45° impact obliquity angle.
The angle of impact (obliquity) of a shell on armor was also immensely important. A perfectly perpendicular strike on armor was the most difficult to defeat while angled impacts acted to disperse the force parallel to the armor, causing a ricochet or greatly reduced damage. This is why armor was angled when possible and where appropriate. Again, I’m grossly simplifying the physics and mechanics of this.
Another important factor that most people are unaware of is just how extensive the armor coverage was. For example, the conning tower of the ship was heavily armored as opposed to today’s ships whose bridge superstructures are not armored at all and consist of what amounts to thin aluminum foil, for all practical combat purposes. Note the thickness (17.3”) of armor around the conning tower of the New Jersey in the photo below.
|Armored Conning Tower|
Critics who think a battleship’s topside would be destroyed by missiles are unaware of the extent of armor. WWII ships were built with armored structures and equipment that we don’t even consider for armor today. The topsides, while not protected as heavily as the hull, were still heavily armored.
One of the common misguided notions is that anti-ship missiles will conduct pop-up attacks and strike the vulnerable decks from above where the battleship is helpless. Battleships were design to defeat plunging fire. From Wikipedia,
The deck armor consists of a 1.5-inch-thick (38 mm) STS weather deck, a combined 6-inch-thick (152 mm) Class B and STS main armor deck, and a 0.63-inch-thick (16 mm) STS splinter deck. Over the magazines, the splinter deck is replaced by a 1-inch (25 mm) STS third deck that separates the magazine from the main armored deck.
Thus, overhead strikes were well accounted for with the upper deck providing the decapping function and the underlying deck providing the main resistance against whatever penetration did occur. Of course, if it were established that overhead attacks were a common staple of missile attacks, a modern version of a battleship could easily redesign the armor to beef up that area.
Anti-Ship Missiles - Now that we understand what is required to have a chance of penetrating battleship armor (meaning an AP shell) and how the armor acts to protect the ship, let’s look at the modern ‘shell’ which is, of course, the anti-ship missile (ASM). ASMs can be crudely grouped into two categories:
Light – typified by the Harpoon (1500 lbs, 490 lb warhead), Exocet (1700 lbs, 360 lb warhead), and C-80x family (418 lb warhead), among others. These are relatively small, light, generally subsonic, and have warheads in the few hundred pound range.
Heavy – typified by the BrahMos (6600 lb, 660 lb warhead), P-700 Granit (15,400 lb, 1650 lb warhead), and P-800 Oniks (6600 lb, 660 lb warhead). These missiles are relatively large, heavy, generally supersonic, and have warheads in the 600-1000+ lb range. Some of these missiles are described as semi-armor piercing, whatever that means.
The obvious next step is to understand how shells and missiles compare as far as their ability to penetrate battleship armor.
Skin – A key characteristic of shells and missiles is the thickness of their ‘skins’. A missile, even the largest, has relatively very thin skin amounting to no more than that necessary to hold the internal components in place and provide an aerodynamic shape. In contrast, naval shells have very thick walls which both aid in penetration and serve to contain and compress the explosive chemical reaction (the blast).
Penetration – The common, light ASMs are not generally claimed to be armor piercing and are, conceptually, simply explosives and motors contained in a very thin skin of aerodynamically shaped sheet metal. They have no armor piercing capability whatsoever beyond their inherent kinetic energy which is woefully insufficient to penetrate significant armor. The armor would not even need to perform its de-capping function since the missiles have no armor piercing cap. The missile would simply explode against the outside of the armor, doing little more than scratching the paint.
Several decades ago, I read reports of tests by the Navy involving launches of anti-ship missiles against armor plates. Unfortunately, at the time, I did not save the reports and have been unable to find them now. As I recall, the missile was the Harpoon. I do not recall the armor plate thickness or composition. Regardless, the result was that the missile achieved no penetration and did no damage.
As noted, some missiles claim to be ‘semi-armor piercing’ but I’ve seen no description or definition of what that means. Presumably, it means it might be able to penetrate some small degree of armor but, unless the missile contains true armor piercing caps equivalent to 16” battleship shells and the rest of the missile body is encased in a thick shell, the missile will have no chance of penetrating any significant degree of armor.
Few – I actually don’t know of any – anti-ship missiles have actual AP noses. Battleship armor is designed to decap heavy, large caliber shells so, logically, an AP missile, if such existed, would also be decapped and prevented from penetrating.
I am unaware of any credible testing of anti-ship missiles against armor. There have been Russian claims but they are unverifiable and Russian claims are almost invariably greatly exaggerated, as the Russian performance in Ukraine has demonstrated.
We noted that battleship critics claim two modes of ‘destruction’ of battleships: Let’s consider the two modes.
Sinking – In order to achieve a sinking, an ASM would have to penetrate multiple layers of armor to reach vital internal areas. Even then, that would not open holes for water ingress. Fire, of course, is always a threat to ships but with vital equipment protected, armor abounding, and extensive compartmentation, it would be very difficult to achieve a sinking.
Mission Kill – As noted, topside equipment is subject to damage but nothing topside is vital. Battleships were designed with armored sensors and had multiple redundant and backup systems so significant impairment of a battleship’s function via topside damage would be extremely difficult to achieve. A modern version of a battleship would have its various radar, electro-optical, infrared, and electronic warfare sensors housed in armored structures as the WWII battleships did with their various radar, fire control, and optical sensors.
A modern version would have many isolated self-defense weapons (SeaRAM, CIWS) each of which has its own self-contained radar. A single hit could not damage much of a ship's defensive weapons. Besides, defense is what escorts are for. Citing the fact that a battleship was sunk somewhere in history does not invalidate the power and survivability of the type.
No ship is invulnerable but a battleship is the least vulnerable ship ever built. A battleship group with Aegis escorts would be an exceedingly difficult group to defeat.
Some might say that this entire discussion is pointless because we are never going to bring battleships back. Well, that may or may not be true but there is a larger point to this and that is the role and value of armor. Whether that armor is applied to a true battleship or to some other type of ship, this discussion reminds us that armor serves an invaluable purpose and should be part of every warship design.
NavWeaps website, “Decapping Revisited”, Nathan Okun,
NavWeaps website, “The Armor Thickness Necessary to Decap an APC Projectile”, Nathan Okun,