The Art of Indirect Fire in the Seven Years' War
A poliorcetic engraving
There is not much information on Simeon Ben Jochai, the Jewish engraver who etched the above image into colored copper. Few artistic professions were open to Jews in most of Germany at the time; printing, lithography, and engraving were exceptions. Like the Jewish cartographers who revolutionized mapmaking in Portugal during the 16th Century, he used sharp details and some creative guesswork. It is small, about the size of a legal pad, and depicts the actual siege of Ziegenhain in 1761.
Voltaire observed that the alliance with the Austrian Hapsburgs against Frederick the Great of Prussia cost France more blood and treasure than the previous two centuries of war against Vienna. The armies of the period were far larger than before, armed with bayonets instead of pikes, consuming huge quantities of everything as they moved, with commensurately higher casualties and at far greater expense.
Logistics were better in much of Europe than they had been during the Thirty Years’ War the previous century. They had to be. France developed the first schools of military sciences, inventing new middle class occupations. On land, this professionalization began with ingeneurs des ponts et chaussées (bridge and road engineers) and systematic use of peasant conscript labor to improve and maintain infrastructure.
Such developments made these new, enormous armies possible at all, yet communications and supply often remained insufficient, especially in enemy territory. For example, Hesse was almost barren of horses or fodder after years of war, making offensive actions even more difficult than usual for an always-outnumbered Prussia.
Feldmarschall Duke Ferdinand of Brunswick-Wolfenbüttel had led the Hanoverian Army of Observation since 1758. Financed by George II, the force included British formations. Moving into the province during mid-winter, Brunswick’s aggressive plan was to bypass the fortified towns of Marburg, Kassel, and Ziegenhain in hopes of breaking the occupying garrisons before a relief force could arrive.
But Victor François, Duc de Broglie, Maréchal de France, led a swift counteroffensive that culminated at the Battle of Grünberg on 21 March. Dependent on a chancy logistical train to the Weser river, Wolfenbüttel withdrew for better country where he might feed his army and find new horses, raising the siege of Ziegenhain two days after the battle. However, he had once again spoiled any chance of France occupying Hanover, accomplishing his primary mission.
Quite apart from their reputation for grim discipline, the Prussian record at poliorcetic warfare, the attack and defense of cities, was uniformly woeful. Frederick was conscious of the weakness and wrote of his efforts to ameliorate it. Yet at Ziegenhain, the execution was flawless. During the sixteen days of investment, 8 heavy guns and 9 mortars fired at least 1,500 projectiles onto a community of just 130 households. One contemporary propaganda sheet reports that Ziegenhain had been “throughout devastated” by the bombardment. “The few houses that are left cannot be mended, and two-thirds of the city lies in ashes from the terrifying enemy fire.”
Despite the destruction, the French garrison refused to surrender and a bloody storming operation loomed. Deliberate flooding slowed progress, yet pioneers were reportedly just finishing their second approach trench when the siege was raised. This is not a bad performance for a siege train in the 17th Century, and for Prussia it was an impressive one, but it was still not enough.
A closer look at Jochai’s artwork reveals some interesting details. Begin with the battery on the left. Two guns firing at once would have been unusual — indeed, the whole point of having a battery of guns behind a protective barrier is to let each crew maintain a steady rate of fire on the target zone at their own safest pace of drill — and the guns would not be placed so close together. But the scene is busier this way, giving some sense of what it must be like to have many guns all firing at the same target together, if not in unison.
As is usual in art of the era that depicts gunpowder artillery in action, only the men firing the cannons are visible “in frame.” If we were to watch the real action here through a time-portal, we would see the gunnery assistants clearing and reloading, as well as mattrosses scurrying about with ammunition and pails of water. These lower ranks of artilleryman have been rendered invisible for the sake of visual simplicity.
Troops march single file down the approach trench in the foreground of the image, muskets shouldered. The zigzag cut of the trench was necessary to prevent the enemy from positioning guns to fire straight down any great length of it. Approach trenches were cut the same way in the First World War to keep a single high explosive or shrapnel shell from killing everyone in the trench. Mortar shells (“grenadoes”) already had shrapnel effects in 1761 and were used defensively on occasion.
As one might imagine, this zigzagging slows the rate of advance towards the objective. Defensive artillery fire and sallies by the defenders can also retard the work of pioneers, spike guns, and otherwise slow down the besieging army. The defenders of Ziegenhain reportedly undertook some spirited sallies at the behest of the townsfolk, though it did not stop the Prussian grip from closing on their city. Serried rows of dots under the defensive walls, above the waterline of the flooded field, are probably stakes of wood or even iron spikes to slow down attacking infantry.
Fortifications exist to slow down attack, but they can only slow it down. If the attacker has infinite time and material means to continue a siege, the garrison is doomed, whether by violence or eventual starvation. Enduring the intense Prussian bombardment must have been an unpleasant experience, but Ziegenhain’s defenders had confidence that the Maréchal de France would move to relieve them. History since then has shown that bombardment rarely ever moves an enemy to capitulate.
For the Prussians, it must have been quite frustrating to abandon Ziegenhain after so much fine work. Ranging on the city from 360 degrees, their batteries were thoughtfully positioned to strike with cannonballs and explosive shells from multiple directions arcing over the walls, potentially striking and setting fire to targets that might be masked from any single battery. This is indirect fire, and if you read certain “military historians,” it is not supposed to exist yet in 1761. The value of indirect fire in the siege role was obvious to everyone and used everywhere. There was simply no tactical need for indirect fire in field battles yet, nor was it possible to aim such fire.
Highlighting this point, steeples and other features around Ziegenhain were used as observation posts to spot the fall of shot so that it could be corrected, though only to a limited degree. Round objects develop random spin as they fly through the air, a phenomenon called the Magnus effect, which adds a measure of imprecision to any gunpowder artillery bombardment with round shot or shells. Nevertheless, the Prussian siege train clearly had efficiency in mind when they set up their bombardment.
One cannot blame them, for every ball or shell they fired had to be made somewhere else and brought to central Hesse. The logistical tail of a siege train was as long as that of an army and half again as heavy. Breaking fortifications took time and numbers, luxuries that Frederick the Great and his generals never enjoyed.