Category: Military History

Do Fortresses Still Exist? Could They?

On War, along with other memoirs and histories of its era, concerns itself in large part with fortresses.  Large, partly self-sustaining fortified areas (food production was always impossible) continued to be important to military strategy even after cannon brought down the old castle walls.

Fortresses had several characteristics:

They controlled strategically important terrain, such as roads, mountain passes, and riverways.  Typically, these features passed through the fortress.

They were large enough to house substantial bodies of troops, materiel, and supplies, well in excess of the permanent garrison.

They allowed armed forces inside to sally and return at will either en masse or in small groups.

They were sufficiently protected, both by fortification and armament, to require a concerted “main effort” to reduce.  Successfully storming the fortress (in modern terms an “assault”, though “storm” is still used in German) required the most effort; an “investment” or siege to prevent sallies and eventually starve out the garrison a lesser effort.  An “observation” or screen could be placed around a fortress with even less resources, although this would still allow entry and exit from the fortress more or less at will.  In the 17th century, an entire field army might be required to reduce a fortress; as armies grew larger this became less the case, but fortresses remained an important feature while declining in importance compared to field fortifications through World War I.

What Happened?

There are two culprits for the decline of the fortress: mobility and firepower.

First, the increased mobility of both mechanized and air-dropped ground forces made it much more difficult for static fortifications to control terrain features.  Motorized and aerial supply lines also make it much more difficult for a bypassed position to disrupt the communications of the bypassing unit.

However, the increased range, power, and precision of modern weapons clearly has the most to do with the decline of the fortress.  Air-dropped munitions can easily destroy most fortifications, and modern munitions will hit whatever can be detected from outside the range of defensive armaments.  The last identifiable fortresses — such as Malta — relied in the final assessment on the inaccuracy of aerial bombs to survive.

What would a Modern Fortress look like?

A modern fortress would have the characteristics described above, but I will add an important qualifier:

It should cost more to destroy than to build.

I won’t get too wrapped up in this, but: if our fortress takes a great deal of effort to create, but can easily be eliminated by a readily-available, inexpensive weapon or attack, it’s not what we’re looking for.

I’d also like to add something else in to make it more specific, based on the concept of “surfaces and gaps”.  A surface is, basically, a strong point (not necessarily a physical location) and a gap is an exploitable weakness.  A surface or gap does not need to always be such to everyone all the time.  An air defense battery presents a “surface” to an aircraft (when it’s turned on!) but a gap to an infantry platoon.

A fortress should be “all surface” to an attacking force.

With this in mind, what are modern equivalents?

Airbases

Both the Donetsk War (Donetsk Airport) and the Syrian Civil War (Menagh, Al-Tabqa, Al-Duhur, Kuweires) have seen airports and air bases hold out against enemy attack long after surrounding territory.  All of these sites had protective perimeter fortifications, and held out far longer than the surrounding territory in the face of enemy attack (in the Syrian case, for several years).  Donetsk did not last as long, but was also not as extensively hardened.

Kuweires

Menagh_Air_Base

Menagh Air Base — The defending SAA occupied the airbase, while attacking rebels operated in the town to the northeast.

500px-Ruins_of_Donetsk_International_airport_(16)

Donetsk Airport in early 2015

One thing that all of these had in common, though, are the lack of an opposing air-to-surface threat.  While the enemy was reasonably well equipped in both cases — including artillery and armor — they had no ability to attack these installations from the air.  In Syria, the government was able to keep the defending forces resupplied via helicopter for several years until defeat or, in the case of Kuweires, relief.

Forward Operating Bases

Expeditionary Forward Operating Bases (FOBs) have many similarities to the airbases above.  However, they are purpose-built to actively support ground tactical operations outside their perimeter, as the examples above are not.  They do include both perimeter fortifications and point-defense systems to destroy incoming standoff munitions.  American “air defense” at bases has mostly been focused on point defense against crude artillery.  Additionally, they may deployed integrated air defense systems (IADS).

CampBastion

Camp Bastion in Afghanistan

Typically an IADS is conceived as protecting an area, but this needn’t be the case.  The Russian military base in Syria at Khmeimim is clearly the protected objective of such a network.  Unlike the typical American FOBs, the Russians clearly consider a sophisticated aerial attack a real possibility.  In accordance with the “all surface” condition above, the defense system shouldn’t require any component outside of the perimeter defense, although this doesn’t preclude the positioning of air defense sensors outside the perimeter, nor the interlinking of the base with a larger network (as indeed is implied by the very term IADS).

Point defenses, however advanced, could almost certainly not prevent a hit from an ICBM or other suborbital attack, but anything short of that remains an open question.  Currently, these air defense systems appear key to the creation of fortress-type installations.

I think it worth noting that any FOB worth its salt has at least limited facilities for air transport, and larger ones inevitably have full-service airstrips.

Tunnel Complexes

On organization that didn’t have the benefit of air superiority was the Viet Cong.  Their most extensive tunnel complexes, I believe, meet the definition of a fortress given above.  The most famous example is at Cu Chi:

CuChi

The tunnels were by all accounts nowhere near as cozy as this illustration implies

This differs from a simple bunker in enabling stockpiling of supplies, providing assembly areas, etc.  Being underground provides both protection and concealment.  The camouflage aspect is most interesting, I think: if every everything that can be seen can be hit, and anything hit is destroyed, then you must not be seen.

Many of the tunnels — including the Cu Chi headquarters — were eventually destroyed.  However, this was not done without an intense, concerted effort, and the tunnels operated for years on end.

The South China Sea Islands

The Chinese installations in the South China Sea (such as the one below in the Spratly Islands) may be the closest modern equivalent to a fortress.  Like the airbases and FOBs above, they have clear fields of fire in all directions (being islands); this is a common feature except for the tunnel complexes.  They’re also large enough to allow critical defense systems some room to move around on the island; only the runway itself is completely fixed.  This need for some local dispersion is also common to the airbases above, and to some degree is even present in the tunnel complexes, which could dig out new tunnels or shift into new areas as needed.

Spraltly_Islands

Chinese installation in the Spratly Islands (Fiery Cross Reef).  The runway is about two miles long.

Cities

Important towns and cities are often located on strategically significant terrain, and may constitute such terrain themselves.  As a result, fortified towns and cities are nothing new.  Unlike the previous examples, seamless perimeter defense appear no longer feasible.  Like tunnel complexes, their defense generally allows for some limited penetration by an attacking force.

Cities are now much larger, relative to armed forces of any size, than in the historical past.  This makes the defense or investment of a city a much more fluid affair than in the past, where city walls and a complete countervallation were standard features of warfare.

21st-century cities are a challenging military problem, but I believe they are better conceived as a complex sort of terrain rather than as a “fortress”, which is fundamentally a “point” position.  An air-defense network could easily cover a large city, but the city itself strikes me as too permeable to enemy attack to constitute a fortress.  However, the terrain of a city could be conceived as allowing for a “fortress”-like strongpoints, providing camouflage.  Such strongpoints are ubiquitous in urban warfare.

The thought of a modern city truly converted into a true fortress is intriguing.  The defender would have to construct a perimeter defense, and the garrison would almost certainly require the mobilization and arming of the city’s inhabitants in an organized manner.  The coordination of the defense would be an incredible undertaking that would probably build on existing law-enforcement and governance structure.  The mass-mobilization aspect runs against current trends towards smaller, professional regular forces; the garrison would almost certainly be outside of the “regular” armed forces structure.  Vague gestures in this direction are sometimes background in science fiction, but nothing like it exists in the real world.  An interesting concept.

Conclusions

The ability both to defend against aerial attack, and to enable the defender to conduct at least limited air operations, looks like a key capability for a modern fortress.  Air defenses have been improving — the ability to intercept both low-flying cruise missiles and high-flying aircraft.  Point defense systems might actually encourage  air defense components to be placed more closely together (by reducing the threat of HARM weapons and the like), encouraging perimeter defenses.  A look at the images above suggests that some level of dispersion inside the “fortress” is another key defensive capability, giving “garrisoned” artillery and air defense systems a space to move around against counterfire.  Defensive dispersion and space for operating aircraft appear to be synergistic: you need a square mile or few to conceal the locations or  your important defense systems, so you might as well have a runway in there.

The necessity for perimeter barriers and clear fields of direct fire (the needed range extended by modern weapons) remains.  The Chinese installations in the South China Sea clearly has these concepts in mind, as do Russian-operated bases in Syria.

 

What Did Clausewitz Get Right?

In a previous post, I talked about what parts of Carl von Clausewitz’s On War I thought had little relevance today.  Let’s look at what has endured.  Once again, I’ll start with the most difficult concepts and save the more trivial or obvious observations until the end.

Critiquing Clausewitz

“Each period, therefore, would have held to its own theory of war…It follows that the events of every age must be judged in the light of its own peculiarities.”

Book 8 Ch 3

While Clausewitz strove for timelessness, much has changed since On War’s publication in 1832, even when he was absolutely correct.  Which perhaps he wasn’t.  Clausewitz’s emphasis on the importance of battle and the destruction of enemy forces has taken quite a beating over the last two hundred years.  The time and geography over which a universal theory of war must hold have expanded, and weapons have become more lethal over a longer range.  I’ll go into some particulars below, and look at what I think is still relevant in a future post (here).

Decisive Battle

“1. Destruction of the enemy forces is the overriding principle of war […]

  1. Such destruction of forces can usually be accomplished only by fighting.
  2. Only major engagements involving all forces lead to major success.
  3. The greatest successes are obtained where all engagements coalesce into one great battle.”

Book 4 Ch 11

“Marches by separate columns and divisions, advance guards and flanking corps, reserves intended to support more than one strategic point, the concentration of individual corps…the small change, so to speak, of the strategic budget, while important battles and other operations comparable in scale may be considered its gold and silver.”

Book 4 Ch 7

The centerpiece of On War, and also the source of its greatest contradiction, is the emphasis the author places on decisive battles.  When he began writing in 1809, Clausewitz’s had a basically unqualified vision of the battle as the path to the destruction of enemy forces, and the destruction of enemy forces as a route to victory.  His service during the campaign of 1812, among other things at least, clearly changed his mind.  He notes how absurd would have been the Russians bringing Napoleon to battle at the border, with the latter at his greatest strength, and the wisdom (albeit, in his telling, accidental) of allowing Napoleon to deplete his strength advancing into the interior.  As in everything else, Clausewitz wisely qualifies the value he places on battles.  He has a much less totalizing view of victory and defeat than those of us living in the post-WW2 world.  An inferior state might win a battle but lose a war; still, in Clausewitz’s reckoning, they would likely put themselves in a better position when they negotiated surrender.  They might even gain easier terms by losing such a battle!   Clearly wars of annihilation, where a country faces the total destruction of its people and institutions as a result of a loss, are not being accounted for properly.

Besides that, is battle truly necessary for victory?  Are guerrilla and rear-area actions simply “small change”?  Vietnam might offer one counterexample.  However, I don’t think it fits; using a suitably nuanced view of Clausewitz, the entire Northern effort to rid the South of American forces might only be considered a shaping effort for the invasion and subsequent decisive engagements of 1975.  Also, Clausewitz does not neglect moral factors in his writing: a loose reading could fit the Tet Offensive into the role of the decisive battle.  The Korean War, I think, makes a better counterexample to Clausewitz: there wasn’t really a single, decisive battle that led to the war’s end state.

Then again, there was a counteroffensive in March 1951 that pushed the Chinese back up to around the 38th parallel.  Was that a battle?  I suspect a suitably stubborn Prussian answer would be that since those actions produced a decisive strategic effect, they constituted decisive battles.  Certainly the rather circular reasoning Clausewitz uses to dismiss certain frictions on the part of an invader support this answer.

Obstacles of this nature [logistical] tend to vanish in the face of decisive victories.

Book 5, Ch 15

After all, battles in Clausewitz’s time lasted for a day, being halted by the onset of nightfall.  This certainly wasn’t the case in 1914, and any adjustments to the concept of a “battle” that can accommodate Passchendaele, Stalingrad, or even Kursk into anything resembling a Clausewitzian framework would allow for COURAGEOUS or TOMAHAWK to count.

I think an answer lies in examining Clausewitz’s rationale for the importance of battle more closely.  He claims, without using the term, that the opportunity cost of other forms of military effort (e.g. deception, feints, infiltration, harassment, turning movements) is too high, that battle – destruction of the enemy’s fighting forces — is always the most efficient method of allocating military effort, with the later qualification of conditions being set.

The North Vietnamese did attempt to shape and fight decisive battles (against the French, Americans, and the RVN).  However, I don’t think their efforts were primarily in that direction.  At best it was one of several lines of effort, and arguably not a wisely managed one.  More recently, the mujahideen who drove the Soviets out of Afghanistan didn’t devote much of their resources to such ends.  Clausewitz does have a ready reply to these examples: they give weaker forces hope, if not material benefit.  Deception, then, is a resort of weakness if not desperation.

Battles – intensifications of combat operations, if not quite like how Clausewitz thought of them – will continue to occur in warfare.  The ability to win battles and to tactically exploit or mitigate victory or defeat is necessary for armies.  Did Clausewitz overemphasize their importance?  Yes.  Sometimes attempting to fight pitched, set-piece battles will produce the desired strategic effect.  Other times, it is foolish.  It is not always and everywhere the coin of the realm.

Eurocentrism

“…at this time the armies of practically all European states have reached a common level of discipline and training. […] It has evolved methods that are common to most armies, and that no longer even allow the commander scope to employ special artifices.”

Book 3, Ch 4

Clausewitz generally speaks only for the European continent, and acknowledges that some of his tenets do not hold outside of the European core where he lived and served.  As a result, he makes certain assumptions regarding conquests, war aims, and politics.  Warfare in Clausewitz’s day was by no means a pretty affair, but the atrocity of the Thirty Years War lay well outside of living memory.  Mass warfare and “peoples in arms” existed, in fact (following the French Revolution) they were the chief innovation of his day.  However, the political and strategic situation in Europe remained, if not static, then relatively balanced.  Even the rise of Napoleon in Europe didn’t fundamentally shift this paradigm; France had always been a major power.  Compare, in Antiquity, the ascent of Athens following the Median War, or even Alexander, as opposed to the Roman occupation.

Because of this relatively stable and insular environment, Clausewitz downplays both the consequences of defeat and the rapacity of conquerors.  Nations defeated in war weren’t exterminated through mass killings, enslavement, or displacement.  Even the most megalomaniacal conquerors contented themselves with obeisance and tribute from the vanquished rather than additional bloodshed.  Hence Clausewitz’s recommendation to weaker states to fight for better surrender terms rather than to avoid total destruction.

Relatedly, Clausewitz assumes relatively static patterns of settlement and demography and can’t account for the strategic impact of mass migration, ethnogenesis, or state formation.  This means he can’t explain the military activities of the New World really at all.  Perhaps Clausewitz considered these political considerations outside the realm of military strategy, but again, they were extremely important to the contemporary military situation in the Americas, as well as (to a lesser extent) in the Far East.  When On War veers towards these topics in discussing the French Revolution or “the people in arms”, Clausewitz becomes noticeably reticent.

Rear Areas and Supply Lines

“Convoys, as a rule, move in the rear of their own army…Consequently, only minor forces can be attached to attack them, which must protect themselves by strong reserves. […] The attack must usually be satisfied with cutting the traces, taking out the horses, blowing up ammunition carts, and so on.  This will halt the convoy and throw it into confusion, but it will not actually be lost.”

Book 7 Ch 18

Rest assured, the destruction of vulnerable materiel is nowhere near this labor-intensive or ineffective nowadays (although the lives of civilian drivers are spared even by the most ruthless partisans more often than one might naively assume).  Repeating firearms and high explosives have made sure of that.  Soldiers in Clausewitz’s day didn’t even have cigarette lighters.  He mostly dismisses damage to supply lines as a waste of effort for regular forces, although he says that irregular fighters (such as civilian partisans) ought to do it when possible.  Aside from the increased destructive power of modern weaponry, modern soldiers must also consider range.  Deep strikes by aviation and over-the-horizon artillery (which did not exist in the early 19th century) also mostly negate the natural ability of the supported forces to protect their own supply lines simply by their presence.  These factors apply equally to operations against rear-area troop billets, which Clausewitz considered rarely effective, much less decisive.

Another major change: lines of communication are much more critical to industrialized armies than to premodern forces.  In the magisterial Supplying War, Martin van Creveld provides quite convincing evidence that the logistical needs of armies from the homeland “base” prior to the First World War were relatively trivial, the primary need being recruits.  Nowadays, armies need spare parts, petroleum, medical supplies, etc. and these must come, eventually, from the homeland industrial base.  Communist revolutionary guerrillas did have some success early in the 20th century by living off of their enemies in these matters.  However, this policy ran into serious limitations in the Korean War and was always of limited applicability.

The bottom line is that operations against lines of communication are both more feasible and more effective than in Clausewitz’s time, although they are not decisive in themselves.

Deception

“Strategy is exclusively concerned with engagements and with the directions relating to them…To prepare a sham action with sufficient thoroughness to impress an enemy requires a considerable expenditure of time and effort…there is always the risk that nothing will be gained and that the troops deployed will not be available when they are really needed.”

Book 3 Ch 10

Clausewitz believes deception to be a of limited use and, again, to detract from the principle focus of winning battles.  As usual he makes some allowance for minor efforts in this area, but clearly doesn’t think it of much importance.  Charitably, Clausewitz may be warning only about the dangers of making demonstrations and feints; probably he believes that the confusion and demoralization inflicted by a successful battle exceeds anything achievable through misdirection.  While it is possible for commanders to overcomplicate plans or misallocate resources in attempting to deceive the enemy, this is true of practically every aspect of an organization’s operation.  Possibly because the matter was outside his specialty and because he never held high command himself, I believe Clausewitz seriously underplays the importance of good intelligence in military strategy.  Other than armed reconnaissance such as that conducted by cavalry scouts, intelligence collection is always smothered in secrecy.  Deception is fundamentally about denying the enemy accurate intelligence, so Clausewitz’s dismissal of the former probably reflects his underestimation of the latter.

Additionally, the increased range and power of modern weapons noted above has made deception more valuable.  The air power of their enemies required Asian armies to develop deception tactics to a very high degree in the latter half of the 20th century.  Similar ruses enabled Serbian forces to minimize the damage from the NATO air campaign of 1998, even though waged by the same air forces that had so thoroughly devastated Iraq’s army less than a decade earlier.  The considerable effort expended on these protective deceptions certainly exceeded the value of accumulating or employing additional combat power.

The Center of Gravity

Probably more has been written on the “Center of Gravity” (Schwerpunkt) than any other aspect of Clausewitz’s writing, so I don’t want to dwell on it too long myself.  That some parts of an organization in space and time are more important than others follows from some basic principles of the universe we live in: a perfectly homogeneous army, with no one part actually more important than the other, almost certainly defies the laws of physics.  In books 4 and 6 Clausewitz refers to major battles as the “center of gravity” of a war or campaign; the more enduring definition he gives in Book 8, Chapter 4:

“The hub of all power and movement, on which everything depends. That is the point against which all our energies should be directed”

He follows with several examples of possible centers of gravity: for great conquerors, their army.  For “countries subject to domestic strife”, the capital;

“[i]n small countries that rely on large ones, it is usually the army of their protector.  Among alliances, it lies in the community of interest, and in popular uprisings it is the personalities of the leaders and public opinion…Blow after blow must be aimed in the same direction…Not by taking things the easy way – using superior strength to filch some province…by constantly seeking out the center of his power, by daring all to win all, will one really defeat the enemy.”

This is a quite “modern” understanding of the concept; although Clausewitz does omit industrial and commercial centers in his examples, his definition does not preclude them, and he does not neglect the “hearts and minds” of counter-insurgency thinking.

This thinking does suggest attacking the enemy’s strength (how do I stop Frederick?  Defeat his army!)  Both sides (or any side) of a conflict have their own centers of gravity, obviously, although Clausewitz speaks of protecting them only through implication, part of a general underemphasis on protection that likely speaks to the characteristics of his era.  Still, protected they are whenever possible, even when they do not actually constitute a military force in themselves.  These include not only the military defenses of a capital, but less tangible means like political indoctrination of cadres.

Anyway, modern theory now appends “critical vulnerabilities” and “critical requirements”, which allow for centers of gravity to be neutralized indirectly (by identifying and attacking those requirements and vulnerabilities).  The resulting concept exceeds Clausewitz’s probably-incomplete musings.

Fortresses

Several points Clausewitz makes I have completely ignored because they obviously no longer apply.  Fortresses – strategically significant hardened defenses – might be of those, but they make for some interesting thought experiments, and are much more clearly a mixed bag of applicability than musings on horse population.

The Composition of Armies

In Clausewitz’s day, armies consisted of infantry, cavalry, and artillery.  Abstracted into mass, speed, and firepower, we still have a reasonably useful way to think about armed forces.  However, the devil is in the details.  In my opinion many modern novelties fall roughly into the realm of “artillery” conceived generally, as they cannot (unlike cavalry) occupy terrain.  Attack aviation, for instance.  However, all of these capabilities are far more diverse than in Clausewitz’s day, when a horse was a horse was a horse. The relative fungibility of troops was particularly pronounced in Europe itself.  Today that an F-22 is not anything much like a P-51, nor an Abrams tank like a Sherman tank, is something we take for granted, but for Clausewitz “saber or lance?” pretty much covered the gamut of technical capability in the cavalry.  The usefulness of intellect, which On War does note, has increased as the result of the complications imposed by technology, a requirement merely to understand capabilities.

The professionalization of support branches like transportation and medical corps was only nascent when On War was written; these are now much more clearly “part of the army” than in the early 19th century.

Conclusion

Some parts of On War have not held up well; much has changed since Clausewitz wrote.  I have not covered some areas which, although of historical interest, are obviously obsolete, except perhaps in passing.  On War is a trove of insight; several times I opened it to dig out a quotation only to realize that the author had anticipated a criticism or that I had not read him with proper nuance.  Still, as deep as the well runs, it is a product of its time and place.  In a future post, I’ll look at what I think are its most useful concepts.

My Impressions of Clausewitz or, “On War” for Dummies

A few months ago I read Carl von Clausewitz’s monumental On War.  A commander I trust told me as a young lieutenant not to bother with it until after company command; I cheated by a few weeks.  I’m writing this to put down my own thoughts while they’re still fresh, while reserving any criticism for a later post (here, and then what I think he’s right about).  Anyone seriously interested in a synopsis of Clausewitz should probably consult Bernard Brodie’s 1976 commentary rather than my own scribbling.

“The Allure of Battle” by Cathal Nolan

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The Allure of Battle, Cathal J. Nolan, Oxford University Press, 2017.  728pp.

In The Allure of Battle, Cathal Nolan purports to tell the reader “How Wars Have [really] Been Won And Lost”.  His basic answer is “attrition”, and he goes a little further and asserts that attempts to resolve wars via decisive battles a la the recommendations of Clausewitz tend to devolve into attrition.  Basically, says Nolan, long wars always end up as wars of attrition, and states that attempt to start small, winnable wars typically end up fighting long wars to their disadvantage.   Over hundreds of pages, Nolan does an admirable job of demonstrating that Napoleon and Hitler were megalomaniacs who pushed their finite military resources beyond any sensible limits, as were other military leaders to lesser degrees.  He ultimately has nothing new to say, unfortunately.

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