War Game: Sinking a Battleship With Tanks

General PurposeAnalytical
Scope and LevelRange of Command Levels
Tactical

Military Services Involved

U.S. Navy, U.S. Army

Type of Operations

Anti-shipping [Hypothetical]

Area of Operations

San Francisco Bay, off Alameda Island

Number of Sides2
Amount of IntelligenceOpen
Method of EvaluationRigid
Basic Simulation TechniqueComputer

Historical Background

As far as I can tell, there have only been a few instances of tanks directly engaging warships. One such example occurred during the Battle of Scheldt in November of 1944. As they advanced into the town of St. Phillipsland, elements of the Canadian Lake Superior Regiment and the British Columbia Regiment spotted several German naval vessels in a harbor across a stretch of water. Positioning their tanks behind a dyke, the tanks (along with other elements) used indirect fire and spotters to engage and sink four Kriegsmarine vessels. Three turned out to be converted landing craft and one was a corvette (Golding, 2014, paras. 1 – 16). That said, it’s important to note that no historical examples involved tanks versus battleships. Given the limited historical examples, I’ve constructed a scenario that defies all logic and elevates the situation into the realm of absurdity…because why not?

Situation

A force of 320 M1A2 Abrams tanks are situated on the former Alameda Air Station field with an Iowa-class battleship (USS Iowa, BB-61) directly offshore to the west of Alameda Island. This scenario will test the effectiveness of the M1 Abrams’ 120mm gun against the armor of a battleship.

Our essential questions are:

  • Can 320 M1A2 Abrams tanks sink an Iowa-class battleship?
  • What information can we gain about the effectiveness of the 120mm gun and its ammo against the battleship’s armor?

Of course, the point of this test isn’t to be realistic or to follow doctrine. Since we’re not focused on examining decision-making or analyzing the data related to the decisions made, this isn’t so much a war game as it is a test of the simulation’s capabilities. Essentially, a test of the simulation itself.

Forces

U.S. Army [Player]U.S. Navy [A.I.]
80x M1A2 Abrams tank platoons (4 tanks/platoon)
(320 tanks total)
1x Iowa-class battleship (BB61) (5320 Damage Points (DP))
Weapons & Ammo:
(per platoon)
80x 120mm M256 APFSDS-T (1 DP)
40x 120mm M256 HE (3 DP)
40x 120mm M256 HEAT (1 DP)
(Total)
6400x APFSDS-T
3200x HE
3200x HEAT
Weapons & Ammo:
0x (all weapons & ammo removed)

Mission

Use the tank platoons to sink the USS Iowa.

Execution

There’s an Iowa-class battleship just offshore …shoot it until it dies.

Based on the DP per round, each platoon can do the following damage:

  • 80 DP of APFSDS-T
  • 120 DP of HE
  • 40 DP of HEAT
  • 240 DP Total

Since the battlship has 5320 DP, in theory, it should take ~22.16 tank platoons to sink the battleship. However, according to Youtubter P Gatcomb (2020), high explosives receive a roughly 20% reduction* in damage done against armored and hardened targets. In his video, he was using high explosive bombs against a bridge, but we’ll assume that reduction applies to high explosives, in general (in this case, tank shells). So, that 120 DP of HE is more like 96 DP. Thus, the adjusted total DP/platoon is around 216 DP. Therefore, it should take ~24.67 tank platoons to destroy the battleship. Whether or not that damage reduction in damage similarly applies to the HEAT rounds is unknown.

*In his video, P Gatcomb says that HE suffers an “80% reduction in damage against armored targets.” However, his calculation of 130 (damage points) x 0.80 = 104 (damage points) is, in fact, a 20% reduction in damage for an effectiveness of 80%. Had it actually suffered an 80% reduction in damage, he should’ve subtracted that 80% (104 damage points) from the 130 damage points. This would’ve reduced the damage done to around 26 damage points. (130 – 104 = 26)

Video

Statistics

Shell Type & Total# Fired# MalfunctionedPenetration Achieved
APFSDS-T (6,400)6,400 (100%)0~65% or less
HE (3,200)2,400 (75%), 800 remaining (10/platoon)47 (1.96%)~20% or less
HEAT (3,200)3,200 (100%)60 (1.88%)~30% or less
For all 80 4-tank platoons combined

Evaluation

My initial testing showed that the initial estimate of ~26 tank platoons was totally insufficient and could not sink this battleship or even cause fires or flooding. As was seen in the video, there were 80 tank platoons and they fired all of their main gun ammo with 10 HE rounds/platoon left when the ship sank, for a total of 800 HE rounds remaining. However, a good number of shells were flying through the air and hit the ship after she was clearly sinking. Although, the fires and flooding probably contributed to some degree to her damage, as well.

Tank Guns Compared to Naval Guns

Tank guns and naval guns are designed for different purposes and to engage different targets. According to William Garzke and Robert Dulin (1985) the armor piercing shells fired by heavy naval guns rely solely on kinetic energy to penetrate armor. A variety of factors influence a shell’s penetration capabilities, but generally they revolve around the diameter and weight of the shell. To achieve good penetrative performance, they fire the heaviest shell possible, but due to their lower muzzle velocities, they sacrifice close-range performance to maximize penetration at long ranges. In contrast, tank guns fire lighter shells at higher muzzle velocities to achieve excellent penetration capabilities at close range. At longer ranges, however, the performance of lighter shells decreases rapidly because they lose their velocity far more quickly. Thus, naval guns fire heavier shells at lower muzzle velocities so that they retain their velocity and armor penetration capabilities at longer ranges (p. 493 – 494).

In summary:

Naval GunsTank Guns
Pros
– Heavier shells retain kinetic energy and penetration at long range.
Pros
– Higher muzzle velocities impart excellent armor penetration at close range.
Cons
– Lower muzzle velocity means close-range performance is somewhat sacrificed.
Cons
– Lighter shell rapidly loses kinetic energy as range increases.

Tank Ammo Capabilities Against Battleship Armor in C:MO

APFSDS

Examining the APFSDS rounds, we again note that each is capable of doing 1 DP according to the game’s database. So in theory, firing all 6,400 of those rounds should’ve been capable of sinking ~1.20 Iowa-class battleships, each with 5320 DP of health. Yet, that was clearly not the case and all of those rounds only did ~60.1% overall damage (3197 DP) to the target. Therefore, each individual APFSDS round did, on average, only ~0.50 DP (50% of their 1 DP). With that in mind, we should also consider that no shell achieved greater penetration than 65% according to the log. Most of them weren’t even close to that level of penetration.

HEAT

For the 3,200 HEAT rounds fired (which should do 1 DP each), they took the Iowa from 60.1% to 77.9% damage (17.8% increase in damage, or ~947.3 DP). So each HEAT round did, on average, ~0.30 DP (30% of their 1 DP). In addition, they caused some flooding and no HEAT round achieved greater than 30% penetration.

HE

For the 2,400 HE rounds fired (which should do 3 DP each, they finished off the Iowa for an increase in 22.1% damage, or 1,175.7 DP. On average, they did ~0.49 DP each (16.3% of their 3 DP). They also caused some fires and no HE round achieved greater than 20% penetration.

This would seem to imply that APFSDS rounds received a 50% reduction in damage done, HEAT received a 70% reduction, and HE received a 83.7% reduction in damage done to the ship’s armor. In other words, APFSDS rounds are ~50% effective, HEAT rounds are ~30% effective, and HE rounds are ~16.3% effective against a heavily armored ship. This calculated reduction in HE effectiveness seems to hold with P Gatcomb’s original assertion, but not his math.

By these new metrics, the adjusted damage capability each tank platoon would be roughly:

  • 40 DP of APFSDS
  • 19.2 DP of HE
  • 12 DP of HEAT
  • 71.2 DP Total

By these numbers: 5320 DP (per battleship)/71.2 DP done (per tank platoon) = 74.7 M1A2 tank platoons to sink an Iowa-class battleship. While this is slightly less than the 80 tank platoons on the map in the scenario, the calculation appears to be close enough to support my initial testing results that roughly 80 platoons were needed.

To summarize the answers to our Essential Questions:

  • Yes, 320 M1A2 tanks (80 platoons) can sink an Iowa-class battleship. Although, only about 300 tanks (75 platoons) would probably be required.
  • The 120mm gun on an M1A2 tank can do damage to an Iowa-class battleship provided that there are enough of them and plenty of ammo. The APFSDS round has the best effectiveness in damage and achieves the greatest penetration. The HEAT round has the second best effectiveness in damage and penetration, and the HE round is the third best in damage effectiveness and penetration.

Alternatives

Barring any changes to the platforms used, some other alternatives to the simulation could be:

  • Altering the scenario so that the tanks can only use one type of shell (Sabot, HE, or HEAT) may produce different results against the battleship.
  • Allowing the battleship to have weapons and fire back at the tanks may produce different results in the scenario.

Additional Thoughts on the Simulation

Although there were no misses, I don’t know how detailed the battleship’s armor is modeled in C:MO or how well we can expect it to be modeled against tank shells of different varieties. (It is known that C:MO doesn’t model certain surface gunfire characteristics like plunging shell fire in ship-on-ship combat.) Furthermore, if C:MO does model the armor scheme with some accuracy, then it’s likely not evenly distributed all around the ship given the fact that the shells didn’t all hit in exactly the same spot and the battleship has an all-or-nothing armor scheme in real-life. This basically means that the most critical areas of the vessel are armored and different types (and thicknesses) of armor are used depending on what’s being protected. It would be silly to expect all of the tank shells to hit on areas where the armor is the thickest. Additionally, the log shows various (less well-armored and unarmored) components being damaged and destroyed by the impacts. This indicates that the tank shells hit all over the ship. What’s interesting is that the HE rounds seemed to cause more damage/round than the HEAT, although that may be because they hit more exposed and less well-armored components.

In the end, I wasn’t really examining how much damage each individual tank shell did on average (aside from the above calculations). I only looked at the overall amounts of damage that the Iowa was sustaining.

It’s also worth noting that WWII solid steel warship armor is different from modern Chobham tank armor, both in composition, and for what it’s designed to protect against. In fact, people have asked why modern warships aren’t armored with anything more substantial than a spall liner. If we can armor a 60-ton main battle tank with composite armor, then why can’t we armor a modern destroyer, cruiser, or aircraft carrier with similar armor? Well, we probably could, but the question is, would it be useful or cost-efficient? Nathan Okun (2002) notes that the face-hardened solid steel armor (such as that on a battleship) is designed to withstand armor-piercing naval shells which travel slower, but farther, than tank shells. Naval armor-piercing shells rely on a cutting or shearing effect to penetrate the armor, whereas tank shells travel at very high velocities and use kinetic and thermal energy to penetrate tank armor which is specifically, and differently, designed to dissipate the thermal effects. Arguably, face-hardened solid steel armor wouldn’t be terribly effective against the high velocities and kinetic and thermal effects of a tank shell because the metal would be heated to a soft and plastic-like state (paras. 1 – 2). So what’s the problem? Well, the thermal effectiveness of composite (tank) armor against high-velocity rounds wouldn’t be of much benefit since naval shells don’t travel as fast. Therefore, the mass and strength of the armor is a bigger factor and designed to stop slower naval projectiles. True, if these composite armors could be protected against the cutting action of naval shells, then they would be, pound-for-pound, better than steel. This lighter composite armor provides good protection against explosive blast fragments and small missiles, but against anything bigger (such as large supersonic anti-ship missiles) it would be prohibitive in terms of weight on all but the largest naval ships (Okun, 2002, para. 4).

What can we derive from this? Well, despite the probable effectiveness of the various tank shells against solid steel armor at such close ranges, it’s worth noting that an Iowa-class battleship is a massive target. The sheer size of the vessel, it’s compartmentalization, and the amount of armor probably compensated somewhat and could explain why it took 320 tanks firing nearly everything they had at it to sink it. (There were 800 HE shells remaining in total, or 10 HE shells/platoon.) Also, note that the sabot and HEAT shells generally were far better at penetrating than the HE shells. Furthermore, although the log doesn’t specify, I somewhat doubt that the sabot rounds over-penetrated the ship. Another thing worth noting is that the Abrams’ 120mm gun is not exactly large in terms of gun caliber, especially when compared to the massive sizes of heavy naval guns (such as the Iowa’s 16″ guns). 120mm is about 4.7″ in diameter, so slightly smaller than 5″ (127mm) secondary guns on the battleship. Even at that, sabot rounds are just a slender, and very dense, metallic dart that relies on sheer kinetic energy to penetrate armor. HEAT rounds rely on directing the chemical energy of an explosive warhead into a thin jet which penetrates armor. In both cases, while they could penetrate the battleship armor to a degree, it would probably be more akin to punching lots of little holes in the armor, whereas an armor piercing 16″ shell from an enemy battleship gun would kinetically punch a large hole in the armor if it penetrated.

At the end of the day, I’d advise people to be very wary of what we’ve derived from this war game. Since I’m not a metallurgist, physicist, or an expert in tank guns, I can’t offer an informed opinion beyond what simple research I’ve conducted. Furthermore, since we’re relying on a simulation to give us data, we’re totally dependent on the accuracy of the programming models. Remember that this wasn’t meant to be a serious analysis and was more of a test of the simulation model itself.

References

Garzke, W.H., & Dulin, R.O. (1985). Battleships: Axis and Neutral Battleships in World War II. Annapolis, MD: Naval Institute Press.

Golding, J. (2014, June 6). Canadians sink four German warships with fire from tanks and infantry weapons. The Maple Leaf. https://regimentalrogue.tripod.com/blog/index.blog/2335701/canadians-sink-four-german-warships/.

Okun, N. (2002, March 27). Notes on Modern Armor. http://www.navweaps.com/index_tech/tech-081.php.

P Gatcomb. (2020, January 15). Command: Modern Operations Tutorial – Bombing [Video]. Youtube. https://www.youtube.com/watch?v=bPVkIPVlNlA.

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