-> It isn't the Marines who want the gun, it is the Navy, and it isn't for amphibious assault purposes either. Geez, for all the work the USN and USMC do together, you'd think they at least could've consulted each other about which are each service's mission requirements, and decide on projects from there. (Question is though, is it really a USN requirement (the USN can't do its job without it), or was it a bunch of Navy Brass and politicians discussing over tails how best to funnel money and keep them in business?) Seems like there are plenty of other promising projects to relegate the AGS to extinction (or to a strictly R&TD project), and let the USMC (and Army for that matter) provide their own long range inland tube-based fire support. Isn't the Navy satisfied enough with TacToms, SLAMs, and any of the coming-soon and projected tactical missiles to provide the more-strategic firepower (>500km)? Always seemed strange to me that they (USN) wanted billion-dollar investments into the AGS system in the idea that longer ranged gunnery keeps the ship out of harm's way (stealthy DDX hull or not), yet wants even more billions for 60-odd LCS platforms that are themselves actually going to be closer to the coastal areas where the USN, in the AGS program, claimed it didn't want to risk sending its big ships into. Does the Navy even know what its own priorities even are, let alone the USMC's primary concerns? ...and for the several-billion per hull for DD(X), would we be further off with new-generation SSGN to follow on from the 4 Ohio converts? I would think that, for almost the same per hull cost, we'd get a much more survivable sub rather than surface ships subject to weather, ASMs, and terrorists. Install a couple hundred SSMs sized from G-MLRS/POLAR to TacTom, and you should do fine. Plus, you're using nuclear propulsion, so thoughts of 30+ years' worth of petroleum fuel operation are out the door. As far as any necessity for surface ships, I can understand the need for a new generation of escorts for CVBGs and USMC Amphib Groups, but DD(X) wasn't really designed for the escort role, was it?

Not a Marine requirement? My guess is that the Navy want the range so as to have the worlds longest range saluting gun then... Seriously though, I think the gun is a sensible thing to have - remember, if your gun can fire 60nm, then you can bombard the beach from 55-60nm, rather than having to get real close. It is all a matter of perception, if the USN can simply piggyback naval artillery advancements on the Army's project funding (i.e. getting the Army to develop the guidance, with the Navy simply applying that to Naval calibres). As for SSGNs, I disagree, they are a useful capability boost, but they are not a replacement for the surface fleet. I would be in favour of the US Navy having around 6 SSGNs, backed by 6 of the proposed Carronade ships, plus the 12 CVBGs (get the carrier fleet back up to full operational strength) and 12 ARGs. This should be supplemented by 12 Surface Action Groups, capable of littoral operations, with an HSV and a few LCS ships, capable of maritime interdiction and mine clearance.

The AGS represents the best weapon option available to conduct strike operations from the Sea within 100 nm, whether it is against maritime targets at sea or ground based targets on land. It is considerably cheaper for the Navy to fire 1200 rounds using precision guidence onto targets on ground than it is for them to launch an airstrike against the same targets. Additionally, the 1200 rounds can be replinished at sea, where the Navy cannot currently replace VLS launched missiles without returning to a port that can support it. Only 9% of the ports in the world can actually do it, and most of those potrs are in Europe, the US, or the Eastern Pacific. Using Iraq as a model, think about this. The Navy could have replaced nearly 50 sorties a day assisting the British marines in the southern Iraq zones with 2 DD(X) ships. This isn't about amphibious assault, it is about precision strike, and from the Navy prespective it is about strike from the sea instead of strike from the air.

For what mission or use does the USN need a 41 to 100 nm gun?

As Galrahn said, Precision Strike. Though they're selling it as a Naval Surface Fire Support system.

The DD(X) and CGX are the direct result of a 1992 “21st Century Destroyer Technology Study,” conducted after Russia imploded. At the time, although the future was clouded with uncertainty, it was clear to Navy planners that future Navy operations would be found in the littoral. As a result, the Navy concluded they would need a new, stealth platform. That is where the concept for the SC-21 (Surface Combatants for the 21st century) came from. The Navy drew up a 70/30 plan, which would be a mix of ships with 70% of the ships being large multi-mission and 30% being small mission specific, and include a high/low mix of ships. At the same time something else happened though, RAND released a study called "The New Calculus..." which was based on lessons learned from the Gulf War. It concluded precision weapons fire could blunt future invasions by destroying up to 20% of the enemy invasion force. The Navy concluded this meant the Navy needed a massive "Arsenal Ship" to provide fires while Joint Air power was moved into the region of conflict. That RAND report is where the concept of "Arsenal Ship" came from. That "Arsenal Ship" became what the Navy called the “Maritime Fire Support Demonstrator Program,” and the Navy pursued the DD-21 “Land Attack Destroyer,” the first of the SC-21 combatants. The concept was approved just in time for the 1997 QDR, which established a future surface combatant target number of 116 combatants. At that time, there were 27 CG-47s and 57 planned DDG-51s, so the Navy suggested the DD-21 replace the 32 legacy Destroyers and Frigates, which is why the DD(X) had such a large number initally. This would establish the CG-47 and DDG-51 as the 70% multipurpose, large ship portion of the 70/30 plan while the DD-21 would be the small single purpose ship. Other SC-21 combatants would follow to replace the CGs and DDGs starting in the second decade of the 21st century. By the 2001 QDR though, things had changed, and the tendency of the Navy to get bigger and better with each platform changed the DD-21 plan. The DD-21 ship became the DD(X), and a CG(X) was proposed. The Navy would pursue the DD(X) and CG(X) to represent the new 21st century force, while the DDG-51s would represent the 'legacy' force to be replaced by the DDG(X) later. For the small combatant 30%, the LCS was introduced. With calls for the BB replacements for fire support, the gun system became the focus of the "Land Attack Destroyer," and the ship was changed from a gigantic stealth arsenal ship into a dual gun platform that included a combination of guns and missiles. It was never about the guns, until the Navy needed it to be in order to justify the size, cost, but most importantly the requirement and relevancy to the US of the DD(X). The guns aren't about the Marine Corp, never were, they are about getting the future 21st century destroyer that represents a quantum leap in innovation for the Navy, everything from 7 RHIBs to 2 helicopters to stealth hull to new electronics to new VLS cells to new power drive to reduced crew to new ship support systems; the DD(X) has been said to do just about any mission the Navy has just to insure the Navy gets their 21st century surface combatant. Without it, the Navy believes they will lose relevancy in the armed services, because it doesn't take much to realize that so far, the most powerful fleet in the world has had only a marginal impact at best in the wars in Afghanistan and Iraq, and the new platform designed to increase impact in the GWOT, the LCS, is a small, cheap ship, not exactly popular among Navy surface fleet officers, which is why some LCS may have non commissioned officers as CO. Keep in mind, amphibious assault wasn't even mentioned in the 2005 QDR, wasn't even mentioned... the first time EVER the QDR or any bottom up review of the Navy didn't even bother discussing amphibious assault as a Navy requirement. With no MEB requirement specified, take note the first thing the Sea Base did was reduce the number of MEBs to 3.9 TOTAL, and only 1.9 at sea on L class ships. The idea the Navy is doing anything for the Marine Corp under this administration is a false premise, otherwise the Navy wouldn't be stealing 1 LHD and 2 LHA from the Marines to pursue the Sea Base, which is basically a Navy commanded and operated 15 ship task force augmented with a civilian crew under civilian specs with minimal defense designed to carry large numbers of troops and equipment into combat. Hope the enemy doesn't shoot back, otherwise the Sea Base is the largest floating graveyard in modern warfare history, because even the WWII era Sea Base had better protection.

I think they ended up getting that 70/30 big ships/little ships ratio backwards: don't they (USN) plan on procuring more LCS than DDX? (I wonder then if that ratio might come down to something more realistic, after budgetary reviews, to be more like 50 LCS/3 DDX?)

The DD(X) will never be more than 2 ships, so it won't matter.

ACtually wish they would not even bother with the DD(X). Put the systems they are developing for it on some old spruance ships to give then the water test, then if they work out, design another generation of ABs that use the systems that work well at sea.

Guess then the USN better start leasing MONARCs from the Germans, eh? Of course, DENEL markets that T6 turret that's suppoed to "Plug-n-Play" with most MBT hulls, so sticking it onto the foredeck of an AB in place of the Mk45Mod4 would actually give the USN at least the 75km range of VLAPs. Better than nothin', I guess (the "nothin'" being the can't-reach-beyond-30km-without-assistance 5" arsenal). But I still don't see the Navy's "need" for it: if they can mount a 155mm L55-60 barrel on a ship and shoot 100 miles, doesn't it logically seem then that the Army and USMC could mount it on a mobile land platform and carry it even farther inland, thus not needing the Navy to do it? (That whole justification thing earlier about the Navy's role in GWOT I think is a rather poor excuse to spend more money on a program whose end goal is already being compensated for by already-well-proven systems: do I really gain any cost savings if I spend several billion dollars in R&D to develop a system that, for the same amount of overall money in the end, I could've easily bought just as many number of rounds of precision-guided missiles as I did precision-guided artillery shells?). The only real edge I see it having is that it might mean the difference between do or don't have boots on the ground: shooting shells over 100km inland (gotta keep the ship a safe distance from the coast) means you might not have to send ground units in to begin with. ...but isn't that where TacToms, SLAMs, JASSMs (and if that RATTLRS ever gets anywhere), and SDBs are best suited anyway? And for the foreseeable future, who do we anticipate will be able to amass large stockpiles of military hardware just ripe for the picking by a gun 100 miles away firing continuous barrages? Against any credible or foreseeable threats, I just don't see any need for one ship to be able to hurl over a thousand shells at distant targets: who will have that many targets to hit that can't be engaged with other assets, and who's going to keep them within 100 miles of their coastline if they know the USN's 100-mile-ranged ship guns are coming? The supporting debates generally seem to be, "if AGS was available here, here, and here, it could've helped whichever units achieve whatever objectives." Hell, that can be said for any number of we-don't-have-them-fielded-yet weapons. And as it seems, whichever of those units did achieve whatever objective adequately enough, without any AGS precision strike capability backing them up. If the USN is so intent on long range precision, why was it "capped off" at a 6" gun and not a larger one, since larger bore does equate to longer range? And please, everybody, no suggestions of it-provides-umpteen-155mm-batteries-fire-support-capability, because a bigger gun has a bigger payload, meaning less shells need be fired (is there some kind of scientific ratio to justify a given caliber and more shells over a larger caliber with less shells?). I still can't figure it out myself, having anything bigger than ship defense guns. I just don't see it coming down to everything depending on one sole ship to shell an enemy for days on end. WW2 ended 60 years ago, and no nation yet has shown itself to be constructing a modern-day equivalent of the Atlantic Wall in preparation to invading their surrounding US-friendly neighbors. The Navy "reasoning" of the AGS sounds fine, only so long as we never plan on fighting beyond its range. Besides, if DDX numbers will be miniscule, I think I'd prefer a system (or systems) that can be retrofitted onto ships I already have, rather than continuing a large investment into a weapon that can only be fitted to just a few ships in my inventory. Besides, if we ever do get to the days of EM railguns, I see no reason why, just like every other tube-fired munitions, that the technology can't eventually mature into being used in weapon turrets smaller than the AGS. Any reason an AB-sized hull couldn't mount a 4-5" rail gun that fires a reasonable range (albeit with a smaller payload)? And did someone yet come out with the specific payload capacity requirements (or equivalent yield) a railgun projectile must provide, to the extent we need a turret and ship the size of DDX to carry it? Was there some subtle international agreement where everyone decided that, "this is the standard for making targets need 155mm shells to destroy them, and everyone will agree to build all their potential targets to this standard"? What if some ingenious developers years from now package some high-tech smart shell with an ideal range/payload that, like many small arms, is discovered to have the best balance in a caliber not common or popular with everybody else? Will people demand it be redesigned (and possibly "de-performed") if it has to adhere to that magical internationally-favored 6" caliber? What if we find out that we're further off using an even larger caliber railgun firing