The Sieges of Alexander the Great Page 4
A further type of ram employed by Alexander was of a simple design, with the ram being mounted on wheels; this could be pushed with great speed against the walls or gates, but was still vulnerable to missile attack from above. This would have been quick to construct in the field and may have been effective against disorganised defenders; the walls could be engaged and the ram withdrawn before they could react effectively and pour fire upon the crews. If a number of such devices were strategically positioned around the circuit of a fortress, a particular crew could attack from any direction, strike the walls or doors briefly and withdraw.
The defenders also had a few techniques in their armoury for dealing with rams; it was common practice to drop large objects into their path, such as boulders or sacks of sawdust. This would delay the approach of the ram and allow the defenders time to bombard it before it could do any damage. A popular tactic was to use grappling hooks attached to ropes to snag the wooden ram and render the weapon utterly ineffective. The defenders always had the last resort of a sally in order to try and burn the siege engines of the attacker. This was a tactic used to great effect against Alexander at Halicarnassus and again at Tyre by means of the fire ship.
Siege Towers
Before the invention of the siege tower, the best, and really the only way for a besieging soldier to get onto the battlements was by using a scaling ladder, as noted earlier. These, of course, were flimsy and prone to collapse, and even when they were of sufficient quality they could not deliver more than one man at a time, which the defenders could easily deal with. Attacking armies needed a way of getting larger numbers of men onto the walls of a fortress, whilst still protecting them from missile fire as they climbed. The first siege towers did exactly that; they were essentially fortified ladders. The siege tower was first introduced to the pages of history at the siege of Motya in 398, here Diodorus describes:29
He [Dionysius of Syracuse] advanced war machines of every kind against the walls and kept hammering the towers with his battering-rams, while with the catapults he kept down the fighters on the battlements; and he also advanced against the walls his wheeled towers, six stories high, which he had built to equal the height of the houses.
As with most new technologies the siege tower is introduced in our sources without fanfare. This is no doubt because whatever the new technology, it tended to be commonplace at the time of writing; this is certainly true of siege towers for Diodorus when he was writing in the first century BC. The first siege towers, then, were wheeled for ease of movement up to the battlements; exactly what provided the propulsive force is less certain. The primary function of this particular tower (and the many more that followed it in later years) was to provide an enclosed space for the scaling ladders, to enable troops to climb to the level of the battlements without fear of missile attack from the defenders on the ramparts as they ascended. The tower also, therefore, needed some form of drawbridge that could be lowered from one of the upper stories to allow the attackers to cross from the tower to the battlements en masse.
Siege towers were a far more flexible weapon than this, however. Soon after the siege of Motya, the two new technologies began to be brought together; towers and catapults. Their very size made siege towers an ideal platform for catapults and archers to reign down suppressing fire upon the walls that would scatter the defenders and allow large numbers of men to gain access to the battlements before they had to fight. This was yet another advantage over scaling ladders, as with them only one man at a time could be deployed and easily attacked at a significant disadvantage as he dismounted the ladder.
The height of siege towers was only limited by the technology being employed by their builders. The first at Motya was, as Diodorus describes, six stories. The towers that Philip II employed at Perinthus in 341 were apparently 80 cubits (37m).30 The most impressive siege towers of our period of study were those built by Alexander at Tyre which were taller than the walls of Tyre themselves, the walls being a reputed 45m. Alexander’s towers were also, apparently, well stocked with siege artillery and protected against fire by flame retardant animal skins. The very size of these towers (Alexander constructed two of them on his mole), are a tremendous testimony to the construction skills of Alexander’s engineers. The towers were no doubt huge, although 45m seems unbelievable, and they would have been extremely heavy. The fact that they were built, under fire from the defenders, on a mole half a mile out to sea is remarkable; the fact that the mole was solid enough to support them is even more so.
We do have surviving instructions from the ancient world as to the construction of the great engineer, Diades’ towers; these instructions survive in the writings of Athenaeus, Vitruvius and the Anonymous Byzantine Historian’s work entitled Siegecraft Instructions. We are told Diades wrote about two general sizes of siege tower, the smallest was 60 cubits high (26.6m) with a base of 17 cubits (7.5m) tapering up its height so that its highest story was 13.5 cubits (6m). This engine was 10 stories high and had a system of internal landings, rather than platforms, to support a staircase; we do not know how many men could be contained within this structure safely, but it must have been very many indeed. The larger of Diades’s towers was apparently 120 cubits high (53.2m) with a base of 23.5 cubits (10.4m) tapering to 19 cubits (8.4m) at the top of its unbelievable 20 stories.31 Diades also recommended that siege towers be covered in animal hide to prevent the obvious defensive tactic of using fire arrows against towers.
We do not have any preserved information regarding the drawbridge or how it was lowered, nor the construction technique required to provide sufficient structural integrity to support the many heavily-armed soldiers that crossed it. We know from Alexander’s career that it was easy to misjudge this, as at Massaga, where many men fell from the drawbridge as it collapsed under their weight, brutally exposing them to missile fire as they lay injured on the ground some way below. Neither do we have any preserved information regarding the base of these towers. We do not know, for example, if it was exposed to the earth, or had a wooden base, making it similar to the other levels. We are told by the Anonymous Byzantine Historian that the smaller of Diades’ towers had six wheels, whilst the larger had eight.
The method of propulsion is also unknown; Xenophon records a three story tower being dragged into position by a team of oxen, but this is a battlefield tower and was not being utilized in a siege situation.32 The tower would have been dragged to a position just behind the main line and used as missile support; catapults and archers could have been stationed on each of its three stories to provide maximum firepower for the space it occupied. Firing down upon an enemy is always tactically advantageous too. This is an extremely interesting tactical device, and one that could have had great effectiveness in some defensive battlefield situations. Darius showed himself capable of using earlier technology in battle by using the, by-then-outdated chariot at Gaugamela. It would have been a very effective weapon for him if these mobile battlefield towers had been employed during his essentially-defensive battles against Alexander. There was no danger of the Persians advancing beyond the towers’ effective range, certainly at the Granicus and Issus as they were set up to defend a river; a few mobile towers stationed at intervals along a river bank could have created great difficulty for Alexander and it would have been interesting to have seen how he dealt with that unique situation.
The team of oxen that pulled Cyrus’ tower, as described by Xenophon, could easily have been moved out of harm’s way once the tower was in position. They would not have been dragging it onto the battlefield under enemy fire. This latter point would be the main problem with using oxen, or any pack animal, to drag a tower up close to a wall; they would present an easy and obvious target for the defenders’ missiles. The Goths discovered this in 537 AD during their siege of Rome. Procopius tells us:33
On the eighteenth day from the beginning of the siege the Goths moved against the fortifications at about sunrise and all the Romans were struck with consternation at the si
ght of the advancing towers and rams, with which they were altogether unfamiliar. But Belisarius, seeing the ranks of the enemy as they advanced with the engines, began to laugh, and commanded the soldiers to remain quiet and under no circumstances to begin fighting until he himself should give the signal.
At the word of command, the Roman defenders showered missiles down upon the oxen and disabled the siege towers. We do not hear of this occurring to any of Alexander’s siege towers during any of his sieges, and so must conclude that they were not drawn by teams of pack animals.
In all likelihood, Alexander’s towers were propelled in a two-fold manner. Firstly, they probably had no floors; this enabled the men inside to stand on the ground and push the tower forward. To enable enough men to push at any given time, a number of crossbars would have been constructed from left to right across the base, against which men would push. The Greeks for a very long time had also had knowledge of the principle of a pulley system to provide a propulsive force; it is easy to imagine a larger number of men positioned behind the towers and pulling on ropes whose pulley would probably have been driven into the ground in front of the tower. A large number of men would, therefore, have been able to pull/push the tower simultaneously forwards towards the fortification. Those inside the tower were obviously protected from the wooden superstructure, while those behind would have been largely protected by the tower itself; missiles fired at an angle could still have reached them, however, once they came within range. It may be that those on the pulley stopped pulling once they got within missile range of the defenders. In order for this system to be effective, the tower would not have contained any men other than those pushing/pulling whilst it was being manoeuvred into position. Any excess weight, like this, would have been eliminated to make the task more manageable with as few men as possible (space within the tower would have been limited too). It is likely that those attacking over the bridge in the towers would have been Hypaspists or Agrianians, specialist troops. The archers were there to denude the battlements of defenders in order to allow the assault troops to gain a foothold.
There is no direct evidence for the use of a pulley system, but we can be reasonably certain that oxen were not used, as Alexander never had difficulty in getting his towers into position, and manpower is the only other real alternative. Space inside would have been restricted, making a secondary propulsion system necessary. We also have to bear in mind that the majority of Alexander’s siege towers were not as large as those described by Diades. At Tyre, his siege towers were undoubtedly huge, but they were fixed in position on the mole, rather than wheeled – the risk of them being pulled or falling into the sea would have been too great for them to have been wheeled. The Tyrians may well have tried to secure ropes to them and drag them, using ships, into the sea if they had not been fixed. Alexander’s towers that were constructed during later sieges on the northeast frontier and in India would have been rather small. We can presume this from the fact that at Massaga the drawbridge broke as the Macedonians were trying to cross, yet we hear of none of them dying from the fall, casualties came as a result of enemy fire as they lay on the ground. The walls, and thus the tower, can not have been very high if the fall was not severe enough to kill. We also know at the city of the Mallians that, after the ladders broke under the weight of hypaspists trying to climb up them to help Alexander, several troops reached the top of the ramparts by standing on the shoulders of a colleague, again telling us that the walls were not tall and thus the towers (where appropriate) would not have needed to be anything like as large as those Diades describes, or as those built at Tyre.
The potential operational use of siege towers made them a perfect weapon for Alexander’s general tactic of attacking an enemy in multiple directions simultaneously. This is a tactic that we see Alexander repeating at every possible opportunity from the sieges of Halicarnassus and Tyre, to the great set-piece battles described in the subsequent volume of this work. At every military encounter where this tactic was possible, large or small, Alexander employed it. One of the great disadvantages of a besieger before the invention of the catapult, and the widespread use of siege towers, was that the defenders could quite easily concentrate their fire against attackers in a relatively small area. Troops climbing ladders could easily be countered, with the result noted above that earlier sieges were almost never successfully carried out by the attacker unless the defenders were betrayed or surrendered because of starvation or thirst.
Siege towers were not invincible, however, as Alexander was to discover several times. At Halicarnassus, Alexander had evidently not taken the advice of Diades regarding protecting towers with animal hides. The defenders, led by Ephialtes, realizing the danger posed by Alexander’s towers and other siege engines, made a sally from the city and succeeded in causing great damage to Alexander’s siege capability, including the destruction of one tower and a number of catapults. Uncharacteristically for Alexander, he made seemingly the same mistake again at Tyre where the Tyrians made clever use of the device of the fire ship to destroy his towers at the end of the growing mole.34 Alexander had not protected them with skins again (he did so for the giant towers he constructed after this). This mistake is likely out of Alexander’s arrogance in simply not seeing how defenders, stuck inside a fortress half a mile out to sea, could possibly hope to sortie against his siege engines with any success. Their destruction at Tyre was a huge setback to Alexander, and depressed him greatly. After a period of contemplation, he resolved to rebuild the mole even larger than before (it had been damaged by a storm too), and to construct giant towers upon it; Alexander never accepted a setback for long. The incident also made him realize his absolute need for a fleet in order to carry the city, as will be discussed later.
Alexander used siege towers to the pinnacle of their operational effectiveness. They spread out the defenders by allowing him to more effectively attack a number of different wall sections simultaneously, and they allowed him to lay down a suppressing fire against the defenders on the ramparts. The coupling of catapults with siege towers led to even greater effectiveness and, together with Alexander’s natural genius for siege technique, led to Alexander being almost invincible in the art of siege warfare.
Siege towers were not restricted to the aggressors in a siege. We see at Halicarnassus and again at Tyre, the defenders made use of siege towers to perform exactly the same role as did the attackers. The defenders in these two instances realized the potential of the besieger’s siege towers raining down missiles onto their ramparts, and indeed within the city, with impunity. The defenders attempted to construct their own towers to be even higher than the attackers, to turn the tables on them, as it were.35 This was an excellent defensive tactic, the fact that it ultimately failed should not detract from its inventiveness. It also implies that constructing the simplest form of fixed tower (they would have had no cause to include wheels) was perhaps no great engineering feat as the defenders of these two cities probably did not have access to the finest engineering minds that Greece had to offer, as Alexander did.
Sapping
Sapping was another traditional siege technique that required no developments in technology to make it possible. This technique involved digging a tunnel underneath a section of wall or a tower, at a relatively shallow depth. This tunnel would be supported by wooden struts at regular intervals, as with a more typical mine shaft. Once the tunnel had been extended underneath the walls, the struts would be set on fire and the ceiling would, in theory, collapse, along with the wall above it. The depth of the digging operation was critical, if the tunnel was dug too deep, the tunnel walls may support the weight even after the struts were burned, and it may not collapse at all. If the tunnel was too shallow then the weight of the walls above ground may collapse the tunnel even before the struts were fired.
Sapping had a number of fundamental drawbacks. Tunnelling was inherently dangerous for the miners; tunnels could collapse prematurely if not properly supported (and even d
espite that on occasion), killing the miners. It may have been difficult to get enough oxygen into the mine to properly burn the wooden struts; if they did not burn properly, the miners could not safely return to the mine to finish the job, as they would almost certainly have burned enough to become unstable. This could be likened to returning to a firework that did not ignite correctly. The most obviously fundamental drawback of sapping was terrain; the topography had to be correct for it to even be attempted. Fortresses that sat upon solid rock were impervious to this technique, whilst those on terrain that was too soft (i.e. swampy terrain or perhaps very fine sand; Gaza was evidently more solid than this) were equally safe.
There were also a number of key advantages to this technique. The minors were protected from attack by the tunnel itself, much in the same way that a siege tower protected those within. The defenders could do little to stop sapping operations, except deal with the consequences in terms of building extra internal walls to protect the city when a breach was formed. Walls could also be brought down from scratch in a relatively short period of time; some of Alexander’s Indian sieges imply that sapping operations had achieved a measure of success after only a few days to a week.
Alexander proved himself to be adept at this form of siegecraft. It was not typically employed on the Greek mainland due to the difficulties of the terrain, but Alexander employed the technique wherever he could. The sources first tell us of Alexander conducting sapping operations during the siege of Gaza in 332. Little is actually recorded save that the operation seems to have begun behind a section of Alexander’s circumvallation in order to hide the fact that these operations were underway. It is hard to see why Alexander felt the need to hide his operations, given that the defenders could do little about them anyway. The Gaza sapping operation was a particular success, although it received only the briefest of mentions in Diodorus. Arrian tells us:36