We’ve been discussing the various aspects of Marine/Navy amphibious assaults with various opinions expressed about types of landing craft and the ability to sustain an assault via air, sea, or a combination. However, the one aspect that we haven’t touched on is the most important one for an opposed assault and that is attrition. While we may not anticipate a full blown D-Day type invasion, the fact is that even a mildly opposed assault will result in significant attrition of the transport assets.
One of our readers, GAB, pointed out that a MEU needs several hundred tons of supplies per day to sustain an assault. I have not independently verified that figure but it sounds plausible and I have no reason to doubt it so, for the sake of discussion, let’s accept it as, say, 600 tons and that’s undoubtedly optimistically low.
Now, I don’t think anyone believes that an assault by a MEU can be sustained purely through the air. If you do think so, run the numbers and you’ll see that it’s not possible. So, for this discussion, let’s look at a beach landing since the water borne transports at least have the possibility of transporting enough supplies to sustain an assault.
The amphibious group that supports the MEU would typically consist of an LHD (Wasp class, 3 LCAC), LPD (
class, 2 LCAC or 1 LCU), and an LSD ( San Antonio Whidbey Island class, 4 LCAC) which provides a total of 9 LCACs. The group also has 10 MV-22s and 4 CH-53Es available for transport. Here’s the transport capacities.
10 MV-22 at 10 tons = 100 tons
4 CH-53E at 15 tons = 60 tons
9 LCAC at 60 tons = 540 tons
Total lift = 700 tons
We instantly note that the airborne contribution is quite limited compared to the waterborne contribution. Nonetheless, the total lift is, indeed, capable of meeting our lift requirement of 600 tons per day. But for how long?
Let’s assume our resupply “lifts” occur in perfect waves and we can manage three lifts per day. Let’s further assume that attrition costs us one transport per lift. What?! No way! Actually, yes way! Hey, it’s an opposed landing. The enemy knows that resupply is the Achilles Heel of the assault. They’ll make every effort to cut the resupply. One lost transport per lift may, in fact, be optimistic. Remember, it doesn’t require a catastrophic kill to attrite the transport. Simple damage that is eventually repairable down the road but renders the transport unusable in the short term is the same as a kill. Further, the LCAC is, by all accounts, a finicky maintenance nightmare. We’ll lose transports to simple mechanical failures in addition to combat losses. Anyway, here’s what the numbers show using an LCAC cargo capacity of 60 tons.
Day 1, Lift 1, 9 LCAC = 540 tons
Day 1, Lift 2, 8 LCAC = 480 tons
Day 1, Lift 3, 7 LCAC = 420 tons
Total = 1440 tons = 2.4 days worth of supplies
Day 2, Lift 1, 6 LCAC = 360 tons
Day 2, Lift 2, 5 LCAC = 300 tons
Day 2, Lift 3, 4 LCAC = 240 tons
Total = 900 tons = 1.5 days worth of supplies
Day 3, Lift 1, 3 LCAC = 180 tons
Day 3, Lift 2, 2 LCAC = 120 tons
Day 3, Lift 3, 1 LCAC = 60 tons
Total = 360 tons = 0.5 days worth of supplies
So, in 3 days we’ve managed to get a little over 4 days worth of supplies ashore and now we have no more functioning waterborne transports.
The same type of effect applies to the airborne lift component except that it starts with a much smaller lift capacity. I leave it to you to work through the math for the airborne component. Also, we should expect a much heavier loss for the air transports given the lethality of Stinger/ZSU type defenses against slow, low helos.
While the airborne transports will help stretch out the supply situation, the reality is that the bulk of the air assets will probably be employed moving troops around and ferrying supplies from the beach to the forward troops and will, thus, have a fairly minimal contribution to the resupply effort.
Now, this was absolutely not a combat simulation. It was, much like the
RAND air combat scenario, a simple exercise in numbers to demonstrate the potential impact of attrition on the sustainability of an assault. You may argue about particular aspects but, unless you make ridiculous assumptions, it won’t change the results by very much. Further, many of the assumptions were overly optimistic. For instance, loss of the transport’s loads when they are “hit” was not factored in nor was any loss of supplies on the beach due to enemy artillery, mortars, missiles, or air attacks. If you factor in a 10%-30% loss of supplies, the results just get that much worse, that much sooner. Also, follow on transport of heavy equipment, as opposed to supplies, further eats into the resupply numbers. Loss of an amphibious ship was not considered.
How many lifts per day can we get? That depends on distance. The farther off shore the amphibious force sits, the fewer daily lifts. I estimated three per day. Maybe it will only be two. Maybe it will be four. It won’t greatly affect the outcome. The assault will stall out in a matter of a few to several days.
Every pre-conflict estimate of supply usage in history has been woefully underestimated. I used GAB’s ballpark supply requirements but the reality is that much more would be needed.
The takeaway from this little exercise is that our concept of how an assault will go is ludicrously optimistic and basically assumes that the enemy will have no adverse affect on our assault. For an unopposed landing that’s fine but even then we seem to have barely enough assets and cannot afford any mechanical losses. For an opposed landing, our assumptions are badly flawed. I don’t see how we can carry out even a moderately opposed landing with the resources and assets we currently have and the doctrine we currently use.
My contention, regardless of what the Marines might say or want to believe, is that the Marines are limited by lift and resupply constraints to being a low intensity, short duration, light infantry assault force. While there’s certainly a use for that type of force, that’s a far cry from the traditional amphibious assault force and begs the question, what role will, or can, the Marines play in an all out, high end war? The answer would seem to be, not much of a role. The follow up question is, given the limited role the Marines seem able to play, can we continue to justify multi-billion dollar amphibious ships?
If you want to comment on this, do it with facts not general platitudes about how important Marines are. Also, please note that this post is an observation about the current state of affairs rather than a statement of position on my part. I’m neither supporting nor criticizing any particular amphibious philosophy. I’m just trying to objectively assess the current capabilities.