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March 05, 2008

Fortifications ....

Mausi's piece a few days ago on the Hohenburg mentioned Sebastien de Vauban, the military engineer who changed the face of fortifications and brought them to the point where assault became so costly it was considered almost impossible - or, at worst, so costly in lives that it was not worth it. That didn't stop wars, but it did change the way places defeneded like the Hohenburg were dealt with. And, like everything else, it led to the development of other ways of attacking such fortresses. In truth, the full impact of Vauban's innovations was not appreciated until well into the twentieth century, and examples of "impregnable" fortresses were still being built in 1939. They include the famous (or infamous!) Maginot Line, the Fort Eben Emmanuel in Belgium and Hitler's Siegfried Line and Atlantic Wall.

So what did Vauban do to fortifications?

Well, he laid them out in the classic "star" design, but he wasn't actually the inventor of this pattern, he took it the next logical step. Instead of building normal walls as his outer curtains and bastions, he built first huge earth and stone embankments. Then he faced these with sloping dressed stone facings, the angle of the wall being around 10 degrees from the vertical as it rose. Atop this he placed firing platforms and embrasures and within the bank built tunnels and huge chambers for storage and accommodation and in some cases built in batteries for cannon and smaller chambers with loopholes for musketry and grenadiers. The angles between bastions and curtain walls were not built at ninety degrees, they turn back slightly on themselves so that the bastion stands away from the curtain and men placed at the angles can enfilade the full length of the linking curtain wall.

Nor could you simply march up to the walls or the bastions, since these are both covered by each other, and fronted by a deep moat or ditch - with an outer bastion standing in front of the inner curtain and filling a space between the inner bastions. More such outer bastions were then placed in front of the main inner ones and are overlooked from behind. In other words, if you succeeded in taking one of the outer bastions, you could not use it to assault the inner one since your occupying force was now exposed to fire from above and behind.

Obviously you have to be able to get in and out under normal circumstances and gates always provide the weakest link in any fortification. Not so in Vauban's designs. The gates could only be approached along deliberately indirect corridors overlooked by embrasures for musketry and grenadiers on both sides. Effectively only the suicidal would even consider trying to send a force up one of these approaches. Even if you got as far as the gate house you found yourself in a tunnel which could be closed at both ends by huge gates and portcullis' and effectively you were now in a kill zone from which there was no way out. As I said, Vauban didn't actually invent most of these ideas, he simply combined them in new and much more effective ways. It speaks for itself that most of his fortresses were never captured by assault, they fell usually after very prolonged sieges and more frequently through treachery.

So how did this influence modern warfare? Well the first thing it did was render all previous forms of artillery obsolete and it led to the development of new guns and more effective siege weapons. One of these was the mortar, a stumpy short barrelled "gun" set in a heavy cradle which fired an explosive "shell" over the heads of the defences to burst inside the fortress. It led too to the development of siege engineering - again, not new, but now taken to a higher degree of science. Ultimately commanders realised that Vauban's fortresses, while superb for defence, did not, in themselves win wars, they simply tied up vast numbers of men which led, in its turn, to heavy losses from disease and starvation on both sides. The answer then, was to fight more mobile wars, to lure an enemy out of these fortresses and fight in open country. A lesson not fully learned until the bloody aftermath of Ypres, the Somme, Thiepval and many, many more attempts to assault the German fortified trench systems in WW1. And that echo of Vauban's fortress design, a design which relied on defences interlocked with others in depth, brought about the development of the modern tank and the heavy artillery we now deploy on battlefields.

Simply walking through one of the remaining examples of Vauban's designs - and there are many of them still in evidence, such as Wurzburg, St Goar and many more along the Rhine and into Holland (Try Sluys on the Scheldt estuary) and in northern France, and you get a feel for the futility of attempting a frontal assault on them. As a military engineer Vauban stands out and his shadow is a long one.

Posted by The Gray Monk at March 5, 2008 09:48 AM

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