It's time once again for our regular Open Thread. Talk about anything you want, so long as it's not culture war.
I'm going to highlight a non-naval military history resource. Nicholas Moran, also known as the Chieftain, is a tank historian, but a really good one. He's also a tanker in real life, and spends a bunch of time on the bits like ergonomics and maintainability that aren't nearly as easy to find in a typical reference book. The best series is probably "inside the Chieftain's Hatch", where he crawls over a historic tank and talks through all of the various features.
He works for wargaming.net, the people behind World of Tanks and World of Warships. I have extremely mixed feelings about them. They're an Iowa sponsor, and I'm grateful for that, as well as for the amount of money they've pumped into military history in general, but I also am not a huge fan of their products. And the less said about their video on the Iowa, the better.
On another note, I'm planning on dusting off some of the "So You Want to Build a Modern Navy" stuff for the virtual meetup tomorrow. Just in case anyone was wanting more of that.
2018 overhauls are Missouri Part 2, Nautical Measurements,* Falklands Part 5, Underwater Protection Part 1, My review of the International WWII Museum and the Standard Type battleships. 2019 overhauls are turret designations, Naval Weddings and wedding decorations, Spanish-American War parts seven and eight and Falklands Part 17.
Comments
Will the LCS Mine Counter Measures (MCM) modules ever be mature enough to be useful? Every iteration of the MCM module design seems to depend on a different unmanned vehicle that’s not ready to be used:
Originally, underwater mines were going to be detected by the Remote Multi-Mission Vehicle (RMMV, aka “Snorkeler-class USV”, an unmanned semi-submersible), but that was cancelled in 2016 due to reliability issues after only procuring 10.
Bottom mines and mines in high-clutter environments were going to be detected by the Knifefish UUV (a small unmanned sub). That system just entered low-rate initial production last year (7 years after being introduced in 2012), and isn’t expected to go into full-rate production until 2022. It’s also battery-powered, so it doesn’t have the range to cover larger areas.
The current plan seems to depend on the MCM USV (aka “Fleet-class USV”, an unmanned 11 m boat), but that program has been in development since at least 2007 and still hasn’t completed testing. I believe the Navy currently only has 3 or 4 of them, with 3 more on the way as part of low-rate initial production that started last year.
In the optimistic case, the Knifefish and the MCM USV are procured in sufficient volumes and deployed on the LCS fleet by 2023-ish, at which point the oldest active LCSs will be 12 years old. In the pessimistic case, late projects keep getting later, or testing uncovers issues which cause the Navy to change its vision for the module yet again.
What’s the likely outcome here? And could this capability have been delivered with less bleeding-edge tech?
European navies all seem to use similar systems, although maybe their standards for "actually working" are lower than ours?
If I were to read only one book about Leyte Gulf/Surigao Strait, what would the recommendation be? Basically I'm hoping for a treatment similar to Shattered Sword for Midway - enough narrative to keep things interesting, without skimping on getting the key technical aspects right.
@Dakkon
As usual, I'm going to recommend Samuel Eliot Morison's Leyte. It's brilliantly written, comprehensive, and doesn't get bogged down in where various people went to high school. See if you can get a copy of the new USNI editions, which have all the errata, plus an introduction by a historian of the period who can point out where Morison is weak.
Other alternatives are Thomas Cutler's Leyte Gulf and Evan Thomas's Sea of Thunder. I read Sea of Thunder north of a decade ago, but remember liking it. Cutler's book is well-regarded, but his prose style drives me nuts. Last Stand of the Tin Can Sailors is deep into the Flags of Our Fathers mini-biography school of history, and really only looks at Samar.
I think a lot of this is that the USN has traditionally not been that concerned with mine warfare. We're a long way from any potential opponent, which makes mining hard. European navies had a lot more reason to be worried about it, and they're usually better at it than we are. WLD-1's failure did leave a gap in USN capabilities, and it's one I hope we close soon. This seems like a problem that should be getting easier to solve. My guess is that they just have higher-priority places to spend the money.
Relevant to last thread's discussion about the Elbonian Navy, this piece is a good look at what happens when you don't leave enough money in your defense budget for logistics and maintenance: https://foreignpolicy.com/2020/08/20/taiwan-military-flashy-american-weapons-no-ammo/
@bean Thanks for the recommendations - I'll check them out.
Mines are not really a blue-water weapon, and the USN has historically not given a damn about anyplace where you can take soundings with a lead line, is generally my view of mine warfare in the USN.
(Though this might not line up with reality at all)
Anthony Tully, one of the co-authors of Shattered Sword, has also written a book on Surigao Strait. I haven't read it (perhaps someone else has, and can comment?), but the Web page is here: http://ww2db.com/surigao
I've looked through a copy, and it's a fine book, but also not what Dakkon was looking for. For one thing, it's about one specific piece of the battle, not the whole thing. And Tully is a great historian, but not nearly the writer that Morison is.
Today, in things to annoy bean, Marine scholarship on reactivating the battleships
This is the perfect setup for a joke on Marine scholarship, which I'm not going to make because I recognize that most Marines do in fact have a brain. The whole thing is kind of a mess. Still no good research on the reactivation costs, and a bunch of chest-thumping about how good the battleships are.
Also, this gem: "During a 1981 Congressional debate, former Secretary of the Navy, John Warner revealed that he was directed to decommission the USS New Jersey (Iowa Class) during the 1973 Paris Peace Accords because "its belligerency and its antagonism was impeding the progress ofthe peace talks" (Vietnam War)."
No, New Jersey was not decommissioned in 1973. She was decommissioned in 1969. This is not hard to figure out.
@bean
It's nice of you not to promulgate hurtful stereotypes about Marines. Even if you disagree with the conclusions, you can see their studiousness in that they prepared this report using only their fine-tipped crayons.
On the navy's not being concerned with mine warfare: overall I feel that the overwhelming force disparity we've had has reduced our interests in employing mines, but we certainly have reason to be interested in detecting mines - the Persian Gulf is 295 feet at its deepest, and we have a habit of sailing around it quite a bit.
It seems there's some suspicion that the Bonhomme Richard fire might have been arson: https://www.10news.com/news/local-news/sources-sailor-possibly-linked-to-uss-bonhomme-richard-ship-fire-under-investigation
Yikes. Between this and Miami, arson might well kill more ships than enemy action.
War on the Rocks had an interesting article recently about shipyard fires. It turns out they're depressingly common, and not limited to the United States and Russia.
Some later US destroyers had half inch plate over their machinery, but were most 5" magazines on light ships entirely unarmored?
I guess when you have a dozen torpedoes and tons of depth charges sitting exposed on the deck it's a bit silly to worry about magazines, really, but the things must have been deathtraps under fire.
The actual combat record of US destroyers doesn't seem to show a lot of magazine explosions. Certainly not in cases like Samar, where the entire hull got shot to Swiss cheese.
I think a lot of it is down to the fact that they weren't using bag powder. Each 5"/38 round has 15 lbs of powder in a brass case. Those are a lot less likely to be set off by a nearby explosion/fire, which tends to make a big difference in the odds of a runaway reaction happening before the magazine vents/the fire is put out by flooding.
I hadn't even thought about that advantage, combined with improved damage control technology and training.
I'll have to re-read your Samar post: can't remember if they dumped their depth charges before engaging.
I don't think they did. Securing depth charges was a standard part of abandon ship drills, because they'd otherwise go off when they fell to their set dept. Torpedoes were considered a real risk, the magazines less so.
The only American destroyer to suffer a combat magazine explosion after 1941 was Halligan, whose magazines were set off by a mine off Okinawa. 1941 saw Shaw at Pearl Harbor and Reuben James as a result of the torpedo hit. I'm not sure how much the DC improvements actually helped here. All three seem to have happened too quickly for the crew to have actually been able to do anything.
The other thing to remember about Samar is that empty magazines don't explode. Several of the DDs and DEs shot off most or all of their 5" ammo, and all of them expended all of their torpedoes.
The Patria company makes a family of armored vehicles called the AMV XP. These are eight-wheeled fighting vehicles that are available in a variety of configurations, ranging from a straightforward APC to complicated electronic warfare vehicles.
One of the variants is a "tank destroyer", which puts a 105 or 120 mm smoothbore cannon on the chassis.
But how would such a vehicle would be used? This thing hits pretty much like an MBT, but it's much more fragile than one, so dueling MBTs with it would be a mistake. So, ambush, maybe? Station a platoon overlooking some place enemy tanks are likely to drive through. But it seems a bit elaborate for a mission that could be done with towed anti-tank guns.
What's going on here?
@Johan Larson:
cannon rounds are cheaper than ATGMs, and it's immune to LMG fire and shell fragments in a way that a soft-skin ATGM carrier (like a jeep/HMMWV) is not? And it can shoot and scoot in a way that a towed piece cannot?
IIRC there's a Stryker variant proposed (but maybe not developed) similar.
The Stryker MGS was the US equivalent. Mounted a 105mm gun, but seems to have not been accepted for full service.
But Ian pretty much got this one. A big cannon is useful for things besides killing tanks in ways that can't be easily replicated by an ATGM.
As for towed guns, those are basically dead. This gives firepower and mobility, but no armor. Firepower alone is a lot less useful. You'd need to get into ambush position way earlier, which makes setting up an ambush a lot harder. That's a role for ATGMs.
I believe Ukraine still uses some towed AT guns (IIRC they signed a contract for someone to provide some updated fire control systems), but I thought that was part of the situation with their civil war where "everything in storage gets wheeled out".
"But how would such a vehicle would be used? This thing hits pretty much like an MBT, but it’s much more fragile than one, so dueling MBTs with it would be a mistake."
Dueling is pretty much always a mistake in wartime; you want to arrange things so that you're shooting an enemy that can't shoot back - either because they don't know you're there, or because you are engaging with a dissimilar weapons system that trumps whatever they brought (e.g. your artillery bombarding their infantry, or your tanks driving through their artillery barrage).
But if you do wind up with a system where you are trading 120mm APFSDS, armor is probably irrelevant. Unless you can arrange for your enemy to buy crappy training ammunition for their modern tank guns like the Iraqis did, any hit is likely to be a kill and the money you spent on armor is mostly a waste.
The money you spent on armor is not wasted if you need to drive through an artillery barrage, or face man-portable antitank rockets and missiles, or the main armament of lighter AFVs. That's where the difference between MBT armor and light-AFV armor matters.
Hence, "tank destroyers". These vehicles are almost as good as tanks for fighting tanks. And as bean notes, they're good for bringing a heavy gun to bear against people who can't respond with anything more than a machine gun or a mortar (presumably standing off beyond RPG range because everybody's got RPGs now). They come up short against a combined-arms force where you may have to face tanks, or artillery, or light AFVs, or infantry with decent ATGMs.
In addition to what others have said, having a big gun on an infantry carrier makes your infantry much more useful in attacking fixed emplacements. A 105mm tank gun firing HEP can punch a big hole in an enemy occupied bunker or building, making it much easier for your people to attack the position.
@bean
I thought the US Army accepted the Stryker MGS as the M1128 Mobile Gun System. Did that not happen?
They seem to have stopped buying them about 10 years ago, before it went into full-rate production. There are some in service, but few enough that the wiki article actually has a count, which is very rare for ground vehicles.
I understand the Abrams actually has something like an immune zone against its own main gun, depending on the armor package. They have had some difficulty destroying irrecoverable ones with direct fire.
The only towed guns left in the US are artillery pieces, and those only because you can lift an M777 with a helicopter.
@Bean
There's nothing in the Solent area you've been desperately looking for photos of for the blog, is there? It's just I'm around the Isle of Wight for the next couple of days. Doubt I'd have time to go and look for anything specific. But if there's something particular you can't find a picture of, I can keep an eye out.
I'm just aware there's a lot of naval/aerospace history around. The old Saunders-Roe factory, a replica Black Arrow, a Type 45 headed out to sea etc.
Anything you happen to run across would be interesting. Particularly coastal batteries, if you can find angles that actually seem to illustrate key features. Mid-range shots are often a problem with those, as the photos are either extremely wide, which doesn't work super-well on later defenses, or very close. And I do really appreciate the offer.
We're starting to see more pushback on the Marine Corps Commandant's 38th Planning Guidance. To recap, in 2019 Commandant General of the Marine Corps, Gen. David Berger released a new set of force planning documents that envisioned a major shift in the way the US Marine Corps conducts operations. Instead of being a "lightweight Army", as it had been during the Gulf War, Operation Enduring Freedom and Operation Iraqi Freedom, the Marine Corps would now be a naval force, oriented around operations in the South China Sea. The goal would be to counter Chinese anti-access/area denial systems by having rapidly deployable US ground units which, in close coordination with the Navy, would stretch Chinese defenses and open gaps to allow the Navy's carriers to operate in the South China Sea. As part of this transition, the Marine Corps is abandoning all of its armor and most of its tube artillery. Instead, the Marines will rely on the Army to provide those capabilities.
Writing in The Strategy Bridge (outline) Jared Simonelli attempts to defend the continued existence of organic Marine Corps armor capabilities. His argument is primarily that the tank is a far more flexible and cost-effective source of fire support for the infantry than aircraft, and will continue to remain so even in the face of advances in unmanned aircraft and precision-guided munitions. He notes that having their own armored forces was crucial for the Marine Corps in World War 2, where during the Battle of Tarawa, naval bombardment was insufficient to displace dug-in Japanese, and tanks were vital in providing both cover and close-range fire support to the infantry against dug-in Japanese forces.
In Korea, after the landings at Inchon, they faced North Korean T-34s on their drive towards Seoul. If the Marines didn't have their own tanks, crucial time would have been lost in waiting for Army forces to catch up. Sheridan tanks along with air support from Corsairs allowed the Marine Corps to continue its breakthrough and secure Seoul in a timely manner.
In Vietnam, Marine Corps light armored vehicles like the M50 Ontos helped greatly during the battle for Hue City, as they were able to allow Marine Corps infantry to better engage dug-in Viet Cong troops in an urban environment. Especially in urban operations, armor has proved valuable because it isn't subject to the same sorts of loiter time and friendly fire limitations as air support. This was true during Vietnam and it remains true today.
Finally, during Desert Storm, the Marines possession of integrated armor allowed them to simultaneously execute an armored drive while conducting amphibious operations to prevent the Iraqi Republican Guard from repositioning. In addition, armor was important in allowing our Marines to travel as fast as our British allies during that phase of the ground offensive, which helped keep the two forces in sync.
Simonelli argues that the notion that tanks are outdated for the Marine Corps results from a misreading of the Syrian Civil War, where Turkish aircraft and UAVs were able to devastate Syrian tanks and artillery with little or no retaliation. However, there is no guarantee that the United States will enjoy similar air superiority to Turkey in a conflict against a near-peer rival. As a result, it's important that the Marines retain some armor capability, so that Marine infantry has an answer to enemy armor in a situation where air support may not be forthcoming.
That said, armor does not necessarily mean the same M1 tanks that the Army uses. Simonelli agrees that the current M1 is far to heavy and complex for expeditionary operations. He advocates that the US bring back the light tank, as a rapid deployable armored vehicle that could accompany Marine infantry on smaller landing craft and provide fire support "on the beach". In this role Simonelli specifically advocates for the M8 Armored Gun System, but I think something like the M1128 Mobile Gun System might also fit the role.
While I agree with many of Simonelli's points, I'm still not sure that the Marine Corps should invest in armor. If the Marine Corps is really all in on its expeditionary basing concept, then I'm not sure that there's really a large role for armor to play. Certainly, I don't think the current Marine Corps leadership envisions the sorts of landings under fire that the Marines conducted at Tarawa or Inchon as being either desired or feasible in a future conflict against China. Either the Marines will be in place ahead of time, in which case a light tank is just a target for enemy aircraft and UAVs, or they'll be going in with assured air support, both from US fleet carriers and their own LHAs.
The one place I could see the Marine Corps having a use for light tanks is in helping Taiwan fend off a Chinese attack. Taiwan is a mountainous island, and a light tank could serve much the same role as the PLA's Type 15 in providing fire support in terrain where main battle tanks cannot operate. However, a situation where the US has to conduct a counter-invasion of Taiwan is a dire one, and I think it makes more sense to invest in both US and Taiwanese capabilities to ensure that such a scenario never comes to pass.
I don't think they should scrap all of their armor because the Expeditionary Basing thing shouldn't take over everything. But I'm also weird and old-fashioned on this stuff. As for the M8, that was cancelled over 20 years ago. We'd have to start from scratch if we want something like that, and given the Marine's record in armored vehicle procurement, that is not a good plan.
The problem is that, at least according to the documents I've seen, the Marine Corps is going to be shrinking by some 12,000 soldiers as compared to the current force. With that in mind, I think the leadership is looking around and asking, "Do we really need that? Can anyone else do it?" With armor, it seems like the answers are "No," and "The Army," respectively. Hence the desire to divest all armor and most tube artillery in favor of rocket forces and things like small amphibious vessels.
I guess my real objection to all of this (not just the divestment of armor, but the whole Force Design 2030 plan) is that it smacks far too much of preparing for the war you want to fight rather than the war you have to fight. It really bothers me that the Marine Corps are explicitly saying that insurgency isn't a thing that they're going to prepare for any more, because if (more like when) the next war does turn out to be another insurgency no one will have prepared and none of the valuable lessons learned in the past twenty years will have been remembered. I've been reading a lot about Vietnam as of late, and one of the big mistakes post-Vietnam in my opinion was the military leadership sidelining anyone who wanted to plan for or prepare for another insurgency because they wanted everyone aligned on preparing for high-end conventional conflict against the Soviet Union. That stance appeared to be vindicated after the dramatic success of the US-led coalition in the Gulf War, but over the longer term, it turned out that the Gulf War was rather the exception.
But of course, I might be wrong. After all, the invasion of Iraq occurred a solid thirty years after the final withdrawal of troops from Vietnam, and during that thirty-year gap, it's difficult to argue that the US got its force structure wrong by focusing on high-end conventional conflict at the expense of counter-insurgency.
Depending on the United States Army to provide a company of US Army main battle tanks to fight alongside a Marine Expeditionary Force or whatever, seems like a bad plan. But having the Army do tank procurement for the Marines seems much more workable. The Army has its own need for light tank-like vehicles for its airborne, airmobile, and light motorized forces, and there would probably be substantial export potential for a vehicle that is USA/USMC standard.
Alternately, if we're not going to build one ourselves, we can buy from a foreign supplier and have the Army manage the procurement.
Also, in the 21st century, a proper light tank-like vehicle is almost certainly going to have a wheeled chassis and so not be properly called a "tank". But, big gun and good mobility enough armor that you need serious antitank weapons to defeat it. The difference between having even a few of those, and having none at all of those, can be huge.
Is there a reason that the Marines would want a lighter tank than the Army? LCACs can handle an Abrams, and the SSC is supposed to have an even greater payload. They take up a bit more space (and tonnage) aboard ship than, say, a MGS, but I'd imagine that the increase in power/protection is worth it.
In my mind the advantage of wheeled tank destroyers is their mobility. They are able to make much better use of roads and bridges, and require less fuel. Why would the marines want to replace their tanks? Have I overlooked some argument in favour of MGS/Centauro like vehicles, or are they interested in being able to make lengthy road marches?
In fairness, not preparing for a war you don't want to fight is a way to participate in the political war-selection process.
"Sorry boss, we can't do that without another trillion dollars and election-losing casualties" works better than "we're prepared, but this is a dumb idea boss".
ofc, it backfires when your boss decides it won't be that bad because you'll be Greeted As Liberators, or the enemy picks the war for you.
Bean, that latest comment about exocets bouncing off a WWII cruiser got me dreaming of nuclear missile battleships again, help!
Is armor against missiles on modern ships not practical because everyone would just start using anti-armor warheads, or are there other reasons? Did you already talk about this in the Build A Modern Battleship series, or elsewhere?
Pretty much. Post-WWII, everyone discarded armor, partially because ships that traditionally had armor were expensive and they wanted to hold down costs, and partially because armor wasn't particularly effective against nuclear weapons. So by the time ASMs like Exocet and Harpoon were being developed, the vast majority of targets were unarmored, and it made sense to optimize against unarmored targets. But if someone were to make a push for armor, then they'd pay a lot more for that than the other guy would to build missiles capable of defeating it. Something like the Belgrano is a weird edge case, and there are other ways of dealing with them.
This has come up in the comments, but I don't think ever as a top-level post.
An LCAC can carry an Abrams, but the largest amphibious assault ships the Marines have access to can only carry three LCACs. If you're standing off a hundred miles offshore, that's all of three tanks for the first six hours of the fight. You'd best hope the enemy is as sleepy as the Nazis at Normandy, in terms of sending their own tanks into the fight.
We presently deal with that by sending 3-4 assorted LHAs, LSDs, and LPDs to support any major amphibious operation, but the proposal is that the Marines should disperse themselves into smaller, leaner forces for fast-paced expeditionary warfare. Or something. If that's the case, there's a good case to be made for something tank-like that you can carry a platoon of on an LCAC. Even better, though it would be a bit of a stretch, something you can sling beneath a CH-53K. Meanwhile, the Army could make good use of something tank-like that can fit into a C-130, because the Air Force isn't really going to send a C-17 into a hot LZ.
..and because the strategic opponent was Soviet Russia, who was making subs and bombers for sea denial, not battleships for sea control (because they intended to win WW3 on land, not on sea). Amirite?
Also, wasn't armor decent protection against nukes? Not if it lands right on top of you, of course, but it does narrow down the required CEP.
Something someone told me a long time ago was that as far as actually making a modern battleship, the one thing that would be hardest to replicate was make thick armor plate. There is simply no industrial process left in place to start from and the hands-on knowledge of how to do it is long gone.
Not exactly. The Soviets actually came the closest to building battleships after WWII (Because Stalin). Yes, there was obviously less need for battleships in a world without a serious seagoing opponent, but I certainly wouldn't rule out something smaller and with, say, 11" guns for nuclear shells as a follow-on in the wonderful atomic future they had planned in the 50s.
Probably less than you'd think. What actually happens to a ship that gets nuked is harder to figure out than you might think (I've looked into it a bit and there's a reason that post hasn't happened yet) but you're looking at damage to the whole ship. You can't really armor the whole ship, so you'll still take lots of damage. Might not be enough to put you out of the fight now, but it will in a couple of hours or days. And flexibility is important for dealing with shockwaves. Armor is not flexible.
@Blackshoe
That is very true. Not to mention that you're armoring against different threats, so even what you had back then isn't 100% what you want to do now. Going to armored ships would be a huge investment, certainly a lot more expensive than asking for a new warhead/missile design.
Barring fighting in the line of battle, what would its utility be in a shooting war with the USSR? Offshore atomic bombardment of Petropavlovsk?
Interesting, looking forward to that. Is there more recent data than Crossroads?
About armor, AIUI it never kept even battleships unscathed, rather it prolonged their time in action. On a modern ship, armor would make it necessary to hit the ship with bigger ordnance (thus more expensive and easier to intercept) and mitigate near misses and shrapnel from CIWS intercepts.
@John
So while you might fit more power onto a LPD with tanks, the more important issue is the capacity of a LCAC, and three or four lighter vehicles work better there. Plus what you say about air mobility. Would it be worth keeping tanks for follow up landings? Or is it best to simplify logistics by operating fewer types, and avoid mixing wheels and tracks?
Pretty much. In practice, they'd probably just use nuclear missiles, which is what they actually did. The American nuclear SAMs also had the capability to attack surface targets, a capability that was seen as important to deal with ships attacking the carrier.
There's some. The problem is not so much the existence of data somewhere on Earth as the data being where I can find it with a reasonable amount of digging.
This is all true, and a good point. The problem is that the armor also makes the ship bigger and thus more expensive and easier to see. To say nothing of having to rebuild armor production from scratch. On the whole, it's not worth it.
@Alexander
If it's just the Marines, definitely best to standardize on a single type.
@Alexander,
As bean notes, the Marines really need to minimize the number of vehicle types, or at least chassis, that they operate. Whether their big-gun vehicle is a heavy tank, a light tank, or a heavy armored car is negotiable, and depends on how much emphasis we're really placing on the lean-expeditionary-force model. And on our actual capabilities for putting various sorts of vehicles ashore.
I will note, since bean is just wrapping up the series, that the British brought eight light tanks and zero heavy tanks to the Falklands. The tanks, while not decisive, were quite useful. A pair of Chieftain MBTs would almost certainly have been less useful even if they could have been landed in a timely fashion, and it's not clear that they could have.
Even if the British had the logistical capacity to bring a substantial number of main battle tanks to the Falklands, I think they still would have preferred light tanks. The Falklands are pretty hilly rugged terrain. In that environment a main battle tank is just going to get bogged down. A light tank (or a wheeled armored vehicle) is going to be much more able to follow the infantry up and down narrow mountain tracks than a lumbering MBT. In addition, the Argentine forces didn't have any tanks of their own (and it doesn't seem like they had a lot of anti-tank weaponry) so the survivability advantage of a MBT is largely moot. In that kind of a situation, you want a big gun on wheels that can help your infantry advance against dug-in opposition, and that's pretty much what a light tank is.
It sounds like they want essentially a SuperAV with a cannon then. Previously I'd thought that heavy combat vehicles were a good fit for amphibious forces, based largely on what you can fit aboard ship. A Ro-Ro full of Chieftains sounds more threatening than the same vessel full of CRVs, or containerised accommodation for infantry. I hadn't considered the advantages of medium/lighter vehicles when it comes to ferrying them to the beach. Infantry clearly have an even greater advantage in that they can be flown ashore.
The SuperAV isn't a bad idea because of commonality, although the armor is a bit light. You don't really need/want amphibious capability, and you do want at least reasonable protection from RPGs. My first suggestion would be to see if they could do a Bradley with a 105mm gun, or whatever ends up replacing the Bradley.
And if you're in a situation where you can use a Ro-Ro properly (pull it up to the pier and unload over a ramp), Chieftains (or Abrams) would indeed be the way to go. But that's very much the Army's territory. The Marines have to worry about getting ashore when they don't have a handy pier, and in that case, your weapons of choice change dramatically.
There is presumably some trade off to be made between more LCACs and more space for AFVs. At one extreme you'd have enough landing craft to transport all your ground forces simultaneously. Alternatively you could carry many more tanks at the cost of requiring many hours to get them ashore. Roughly how many trips must an amphibious warfare ship's landing craft make to unload it? How do you find the right balance?
Coming in late but just wanted to chime in about the MGS. I've been doing a lot of reading about modern US armored doctrine and my understanding is that the original idea was that the MGS would be scattered around Stryker infantry battalions as a kind of infantry support gun, kind of like how the Germans used Stugs during WW2. For reasons I haven't found yet doctrine was changed so that the MGS got slapped together with the Anti-Tank strykers (the variant with the TOW launchers), who used to be in their own anti-armor platoon, and handed over to the Calvary squadron (IE the recon part of the stryker brigade combat team) as a weapons troop. This somewhat parallels the Calvary receiving their own tank company in the Armoured Brigade Combat Teams.