This paper addresses the issue of how water played a role in ancient conflicts, from the poisoning of water sources to flooding, to stop the advance of enemy armies. It deals with military actions quoted by several ancient Greek and Roman authors, who in some cases narrate these experiences first-hand. Although many abhorred such actions, they were considered tactical expedients to resort to, as cited by the war manuals of the time. The analysis starts from the ‘manual’ Strategemata of Sextus Julius Frontinus, in addition to other references left by historians and chroniclers of different periods. It continues with the evaluation of the impact of the intentional actions of water contamination described by the ancient authors, according to present toxicological and health knowledge.

INTRODUCTION

For more than 2,000 years water resources and related infrastructures played the role of ‘target’ or ‘weapon’ in several conflicts, both among States and in random aggressive actions conducted by terrorist groups. Since there is no substitute for water, a shortage or the impossibility of using it for any reason (blockage in supply or contamination) implies that the communities targeted suffer damage, sometimes irreversible.

At the same time, water can be used as a useful defensive element (ditches) but also in an offensive manner, such as floods triggered ad hoc. We may therefore conclude that water has always represented, despite the rules set at international level (e.g., the Geneva Convention of 12 August 1949), a factor still present in regional conflicts, as seen in the 20th century (Gleick 2004). Starting from the classical authors, the involvement of water as a weapon of war is examined and also the effects on the level of perception and the ethical implications.

MILITARY SCIENCE DESCRIBED BY THE CLASSICAL AUTHORS

The Greek City States, since their inception, in order to ensure their development and even their survival, had to have an organized armed force. Their ranks were formed by full-time soldiers and drafted citizens. The organizational aspect was, in any case, decisive, as cohesive and ordered units are always more incisive than a multiplicity of valiant duelists individually scattered on the battlefield. In short, there is a need for a ‘military science’, also known as the ‘Art of War’, which in a Western context originated in Greece and was then taken up and enriched by the Romans and later by the Byzantines, over a period of time of almost two millennia.

With reference to the period prior to the fall of the Western Roman Empire (ad 476), there are several different writers of western military art who have left important evidence (Le Bohec 2000). Among these, there are famous generals like Thucydides, Caesar, and Frontinus, with his manual Strategemata, which will be a matter for subsequent discussion. Also to be taken into consideration are scientists/engineers such as Philo of Byzantium and Vitruvius (tenth book of De architectura), who with their studies on war machines made important contributions to the Poliorcetica, or the art of conducting sieges. Close to the fall of the Western Roman Empire, the Byzantine Publius Flavius Vegetius was entrusted by the Eastern Roman Emperor to rethink the art of war after the heavy defeat suffered at Adrianople in ad 378 by the Visigoths. The text of Vegetius’ Epitoma rei militaris, although with a series of objective limits due to an analysis excessively focused on the past, had in the Middle Ages vast fame in the western part of the Empire (Breccia 2011). In the east it influenced Byzantine military treatise writings until the 6th century ad, when the Strategikon of Emperor Mauritius became the main reference of the military elite (Luttwac 2009).

War tactics and the role of water

The Romans, even more than the Greeks, had a cultural reluctance to wage a war ‘more latronum’ (by the custom of brigands) which resorted to ambushes, betrayals, night attacks, or various devices. The oldest military ethics praised fighting face to face, called ‘bellum iustum’, without deceit; in fact, Achilles was the prototype hero, unlike Ulysses who was instead sneaky (but successful). However, from the Second Punic War, the Roman commanders began to change attitude, since they had to counter the tactical genius of Hannibal, the master of unethical but winning strategies. The person responsible for the change was, in fact, the general Quintus Fabius Maximus, who on several occasions used deception to achieve decisive results to damage the Carthaginians (Brizzi 2002). This new way of war is described in the manual of stratagems written by Frontinus in the 1st century ad. Among such actions, the deliberate contamination of water sources, as described below, has to be included. In the text of Frontinus, no examples involving the use of poisons ever refer to the Romans; it was the historian Publius Annius Florus who made us aware of this kind of attack.

The Roman general Aquilius, sent in 129 bc (before Frontinus) in the newly formed Roman province of Asia to suppress a rebellion that was spreading, did not hesitate to contaminate the water in the besieged cities (including Pergamum). In this regard, Florus harshly condemns this action: ‘Aquilius finally brought the Asiatic war to a close by the wicked expedient of poisoning the springs in order to achieve the surrender of certain cities. This, though it hastened his victory, brought shame upon it, for he had disgraced the Roman armies, which had been hitherto unsullied, by the use of foul drugs in violation of the laws of heaven and the practices of our forefathers’ (Florus, Rerum Romanorum, Book I, 35, 7). There was an interesting analysis conducted in the 17th century by Hugo Grotius, Dutch philosopher and jurist, on documents of Greek and Roman historians. In this analysis, Grotius shows that for the Romans (unlike the Greeks), water contamination was always considered a despicable action, and in this regard he stated it ‘.to be not only contrary to ancestral custom but also contrary to the law of the gods; just as we have pointed out elsewhere, writers frequently ascribe the laws of nations to the gods’. Grotius, however, specifies that for the ancients not every use of water in war is to be condemned as ‘This is considered to be like the diverting of a river, or cutting off the veins of a spring, which is permissible by nature and by convention’ (Grotius, de Jure Belli ac Pacis, Book III, 4, 16–17).

If the poisoning of water was a matter of shame for the Romans (probably the reason why the tactics of Aquilius are not mentioned by Frontinus), for the Greeks it was a generally accepted military practice, described and encouraged by their ancient strategists, as appears evident from the oldest military treatises (Tacticus, Poliorketika, Chapter VIII).

SEXTUS JULIUS FRONTINUS: FROM WATER TO STRATAGEMS

Sextus Julius Frontinus (born in ad 40 and died in ad 103–104) began his political and military career in Gaul and then in Brittany. Subsequently, according to the official use of the Roman administration that alternated civilian and military task assignments, Frontinus became, in ad 97, the Curator Aquarum of Rome, a role that required the best technical and organizational skills, typical of an experienced military commander. This allowed Frontinus to write De aquaeductu urbis Romae, to date, the basic text for the study of the ancient aqueduct systems and for which Frontinus is still very popular. The vast technical experience at his disposal along with an undoubted talent for manuals allowed him to also write a military art treatise De re militari. Of this work, only four Strategemata books have been preserved, containing a large collection of military anecdotes, or stratagems used by the generals of the past. The water references are mostly found in Book III, Chapter VII, covering De fluminum derivatione et vitiatione aquarum (On diverting streams and contaminating waters) and illustrates how a good Roman general should take into account the importance of water in planning and conducting a military campaign, and especially in sieges.

The following situations examined relate to examples suggested by Frontinus but also by similar incidents that occurred in various geographical and temporal contexts: in particular, contamination and poisoning, water energy as a means of war, the type of water infrastructures to storm cities, and water as a logistical factor for troop services.

Intentional contamination of water

Attacks of this nature, clearly more effective if the water is not abundant, are found mainly in the Middle Eastern area. The Assyrians (Ostfield 2004) in the 6th century bc employed ergot (Figure 1). The hallucinogenic and gastrointestinal colic effects on unsuspecting drinkers were so severe as to inhibit their fighting capabilities.
As to this type of attack, Frontinus cites one ‘non-Roman’ example, which is the conquest of the city of Cirra by the Delphic League during the First Sacred War (5th century bc). On this occasion the water resources used by the besieged population were contaminated with hellebore roots (Helleborusniger), as shown in Figure 2. The active ingredient, helleborine glycoside, caused such violent gastrointestinal reactions as to incapacitate the defenders. This military action is considered exemplary, because it is widely cited by other ancient authors, Polyaenus (Stratagems, Book VI, 13) and Pausanias (Periegesis Hellados, Book X, 37, 6). The latter author points out the Athenian Solon as the inspirer of the operation. This type of military action would be normal practice in the wars among the Greeks, to the point that it was also indicated in connection with otherwise inexplicable deaths within the population. For example, the Athenians accused the Spartans of having contaminated the water supplies of the Piraeus, which triggered a serious epidemic that in 430 bc killed more than a third of the population, Pericles being one of those to lose his life. On this matter Thucydides says ‘It first attacked the Inhabitants of the Piraeus, and it was supposed that the Peloponnesians had poisoned the cisterns …’ (Peloponnesian War, Book II, 48, 2). Although Thucydides does not confirm this conjecture, what emerges is the panic that spreads among the population, a real mass psychosis that always requires a guilty party.

General Belisarius, who as a Byzantine was the synthesis of the Greek and Roman art of war, did not hesitate to resort to this system during the siege of the city of Osimo in ad 539 (Procopius, Bellum Gothicum, Book II, 27) when he ordered to be thrown into the water tanks that fed the city, dead animals, herbs, and quicklime. Such action, however, did not give rise to significant results, so much so that after a few months the besieged Goths agreed to surrender because they were ‘driven by hunger’.

In continuity with the Greek tradition, we can see that in Strategikon, the Byzantine reference military text, the intentional contamination of water is a normal practice. ‘The general is expected to develop plans to defeat the enemy not only with weapons but also with food and water, making the water undrinkable and poisoning the wheat’ (Mauritius, Strategikon, Book VIII, 2, 99), thereby overcoming previous doubts and criticisms.

There is another episode described by Frontinus (Strategemata, Book II, 5.12) relating to chemical and biological attacks linked in some way to drinking. It is the stratagem used in the 3rd century bc by the Carthaginian general Maarbale (also in this case a ‘non-Roman’) sent to put down a revolt that had broken out in the territory of Libya. The general engaged in a skirmish with the rebels, simulated a retreat, and left in the abandoned camp wineskins mixed with mandrake (Figure 3). A few hours later Maarbale, who knew the inclination of his opponents to drink wine, returned to wipe out the rebels who had fallen into a deep sleep after drinking too much in celebrating the easy victory. The adulteration of wine, the taste of which can easily hide the presence of foreign/harmful substances, is an action seen many times in history. A century before, a similar ploy was adopted by the Celts against the Autariati, an Illyrian tribe that had settled in the Balkans, against whom they were in perennial conflict. As the Greek Polyaenus reports in his war manual, similar in the setting and title to that of Frontinus, the Celts used unspecified ‘poisonous weeds’ that produced violent laxative effects that inhibited any possibility of resistance (Polyaenus, Stratagems, Book V, 42).

The widespread fear caused by water poisoning has also been used to persecute ethnic and religious minorities. This happened in the Middle Ages when the so-called ‘poisoners of wells’, belonging to the group known as the Jews, were held responsible for the spreading of the Black Death. Thousands of them died during riots caused by hysterical reactions. This took place mainly in central Europe: famous are the 1349 Elfurt and Mulhausen ‘pogroms’ (Glenisson & Day 1970). Also, the cruel methods of torture then used against the accused and the alleged reduced spreading of the disease due to a greater isolation of the Jews and to hygienic and religious practices, meant for many people a proof of guilt (Foa 1992).

The Appendix (available with the online version of this paper) examines, in the light of current knowledge, the toxicological and health aspects related to the different types of contamination described.

The energy of water as a weapon of war

The episode involving the Romans, and quoted by Frontinus, refers to a military action that took place during the Iberian Wars (143 bc) when Quintus Caecilius Metellus Macedonicus was governor of Hither Spain. During a military action against the Celtiberians, Metellus managed to gain victory by flooding their camp located in a valley. This result was achieved by diverting the course of the water located at an altitude higher than the enemy camp, and by suddenly releasing the waters. Previously, a similar action was used by the Spartan King Agesipolis during the siege of Mantinea in 385 bc, a city hostile to Spartan hegemony. The Ophis River flowing near the city was diverted in the direction of the walls. These walls, built with green bricks, began to crumble, forcing the inhabitants to surrender (Pausanias, Periegesis Hellados, Book VIII, 8, 7). In a similar way, the intentional flooding of lowlands became a useful tactical action to slow down the march of invading enemy armies. The Romans under Emperor Julian (called the Apostate) in ad 363 went through a similar experience during the military campaign against the Persians-Sassanids. Near the city of Birtha (the current Tikrit in Iraq), the advance of the Roman troops was stopped by the flooding caused by the Persians through the irrigation system fed by the Tigris River (Ammianus, Rerum gestarum libri, Book XXIV, 2, 10–11). On this subject another ancient author says, ‘…and went through a place, where was a morass formed by art, the Persians having imagined that by cutting a sluice to admit the water of the river, they could form an insuperable obstacle to the passage of the army by that route’ (Zosimus, Historia Nova, Book III, 19). At the end, this military campaign that had seen the Romans prevail in all pitched battles, was a complete failure. The Roman troops withdrew, exhausted by the logistical difficulties due to their deep penetration into enemy territory and ongoing guerrilla actions by the Persian army. The emperor himself was killed in a skirmish with Persian knights on the way back.

Deliberate flooding has been used through the centuries and has come down to us, with often different results. During the Renaissance, the revived attention to hydraulic issues brought about a study of this type of military action as seen in a drawing (Figure 4) by Leonardo da Vinci, describing a sluice specially designed to release sudden floods (Barsanti 2015). Filippo Brunelleschi, the well-known architect of the Dome of Florence, in 1430 developed a project to divert the river Serchio and flood the city of Lucca that had been besieged for a long time by Florentine troops. However, the unexpected sinking of a bank of the new canal caused an uncontrolled outflow of water, so it was not the town that was flooded but instead the camp where there were the Florentine troops that had run away (Machiavelli, Discourses on Livy, Book IV).
Figure 4

Floodgate to cause flash floods by Leonardo da Vinci (Manuscript B, f 64r Biblioteque de l'Institute de France, Paris).

Figure 4

Floodgate to cause flash floods by Leonardo da Vinci (Manuscript B, f 64r Biblioteque de l'Institute de France, Paris).

One of the greatest war theorists, Carl von Clausewitz, classifies intentional flooding among tactical defensive actions, citing in particular an episode during the French–Dutch War of 1672. When the troops of King Louis XIV of France crossed the border, the Dutch, by opening the dams, flooded the invaded territories, forcing the opponents to retreat (von Clausewitz 1976: Book VI, 20b).

However, the most devastating example of this type of defensive action goes back to the last century, when in 1938 during the Sino–Japanese War, the destruction of the Yellow River embankments carried out by the troops of Chiang Kai-Shek trying to stop the advance of the Japanese, produced as ‘collateral damage’ the death of about half a million Chinese not informed of the operation.

The construction of tunnels and passages through the aqueduct

Digging tunnels is a topic alluded to by Frontinus in his treatise when he talks about sieges (Strategemata, Book III, 8). Digging tunnels to pass under fortifications or to make walls fall down were the first techniques used by the Romans. The Roman army conquered (436 bc) the Etruscan city of Fidenae (Livy, Ab urbe condita, Book IV, 22) with a tunnel under the enemy's walls.

The digging of a tunnel was a long, hard job, and was exposed to the risk of interception by the besieged force; it was certainly far faster and less risky to use a pre-existing underground passage, consisting of an aqueduct. It is obvious that if a passage were available, especially if not adequately monitored (or obstructed), it would represent a weakness in the defenses of the city.

One of the first examples of this use is found in an episode that took place in 219 bc during the Social War between Philip V of Macedonia and the Aetolian League. A ‘commando’ unit of 20 Aetolians entered the city of Hegira passing through an aqueduct, neutralized the guards at the entrance, and opened the doors for their comrades who were waiting outside the walls. This initial tactical success was soon overthrown, because the Aetolians, who were immediately interested in ransacking, did not consolidate the conquest of the city, thus giving the inhabitants time to regroup and chase away the Aetolians who had entered (Polybius, Historiae, Book IV, 57 8).

Another example is offered by the Gothic War between the Eastern Roman Empire and the Goths, accurately described in the work of Procopius of Caesarea, historian and adviser/secretary of the Byzantine, General Belisarius. The city of Naples, which in ad 536 was allied with the Goths, was besieged by General Belisarius (Procopius, Bellum Gothicum, Book I, 9) and was conquered thanks to the covert entry of a group of 400 soldiers through an underground tunnel which was part of the ancient Greek–Roman aqueduct of the ‘Bolla’ used to take water to the city. Sometime later, during the same war campaign, General Belisarius, but this time as the besieged, was successful in foiling an attempt by the Goths led by their king, Vitiges, to enter Rome through the Virgo aqueduct, the only tunnel still functioning since the other aqueducts had been cut off by the Goths. A sentry noticed some Goth explorers inspecting the tunnel, which was immediately barred (Procopius, Bellum Gothicum, Book I). Having failed in this last attempt, the Goths, after more than a year of unsuccessful siege, retired in March of ad 538.

Another important city, Constantinople, surrounded by imposing walls, was conquered with this stratagem. Justinian II Rhinotmetus (named thus for having his nose slit after his deposition in ad 695) tried, in ad 705, to conquer the city from which he had been driven out. In order to accomplish this he took advantage of an ancient aqueduct that passed under the walls (Dalbon 2014), escorted by a group of followers. Once inside the city, they were able to open one of the gates and let in the Bulgarian troops who had accompanied them, and so Rhinotmetus was able to regain the throne.

Returning to Naples being under siege, it is interesting to consider that in 1442 the Spanish nobleman Alfonso of Aragon, who had knowledge of Procopius’ writings, after brief research was able to locate an underground passage in the same way as Belisarius. Thus, the city was taken from the Angevin king (Miccio & Potenza 1994).

Water has also been used to counter the construction of tunnels designed to pass under surrounding walls or make them collapse. One of the systems used was to flood the perimeter moats to defend the fortifications. Julius Caesar himself (Bellum Gallicum, Book VII, 72) used this strategy in Gaul when he arranged to deflect a shallow stream to fill the moat surrounding the military camp from which he put the city of Alesia under siege (Figure 5). The effectiveness of ditches to counter the construction of tunnels by the besiegers was codified by Flavius Vegetius (De re militari, Book IV, 5) in his work on military tactics.
Figure 5

Scheme of the fortifications of the Alesia Roman camp.

Figure 5

Scheme of the fortifications of the Alesia Roman camp.

Water and logistics: water supply for the troops

Square-shaped Roman military camps have always been admired for their rationality and have thus become the founding plans for permanent fortresses (Figure 6) and also for cities. According to Frontinus (Strategemata, Book IV, 114), the idea was derived from a study of a camp that Pyrrhus had abandoned after the battle of Benevento in 275 bc. Water was a crucial element in determining the location of a camp; in fact, the commander had to make sure that from one of the four sides they could get ‘water and forage’ (Polybius, Historiae, Book VI, 25–32), since soldiers and animals were equally important in military campaigns.
Figure 6

Example of the Roman camp of Templeborough near Rotherham, UK (drawing from: http://www.sheffieldhistory.co.uk).

Figure 6

Example of the Roman camp of Templeborough near Rotherham, UK (drawing from: http://www.sheffieldhistory.co.uk).

For the supply of water for detachments operating in areas with scarce natural water supplies (Polyaenus, Stratagems, Book IV, 6), it was carried in wooden barrels (water casks) by wagons (Figure 7) accompanied by armed escorts to repel possible attacks. Cassius Dio (Roman History, Book LXV, 5) reports that during the siege of Jerusalem patrols of Jews, passing under the walls of the city through a network of tunnels, ambushed especially water carriers, who played an important role in the logistical support of the besieging Roman troops.
Figure 7

Wagons for the transport of water from Trajan's Column in Rome (assembled by Renato Drusiani).

Figure 7

Wagons for the transport of water from Trajan's Column in Rome (assembled by Renato Drusiani).

When this water had to be preserved for long periods, the Byzantines recommended putting it in barrels along with river gravel and keeping it moving. This was done thanks to containers that were slowly filled by the dripping of taps placed at the bottom. Once full, the containers were from time to time poured into the main container. If symptoms of water spoiling appeared, it was suggested that small amounts of vinegar were poured into the barrels (Mauritius, Strategikon, Book X, 4).

CONCLUSIONS

When Shepherd, in the late 18th century, translated from the ancient Greek the text of the Stratagems by Polyaenus (2nd century ad) revealing how – in different ways – water could constitute a strategic weapon to resolve conflicts, in the preface he explained that ‘The stratagems would help the generals who were at that time establishing the British Empire in India.’ Today, such a wish could hardly be reconfirmed, for technological evolution has occurred and ideological reasons were the basis of Shepherd's advocacy. Some elements, however, still remain.

Above all, in more than two millennia of history crossed by conflicts of various types and sizes, water continues to represent one of the possible components in such conflicts. Compared to the past, military action involving water is strictly banned by international treaties and agreements, and for this reason is mainly confined to ‘asymmetric conflicts’. Another element which has instead remained unchanged over the centuries for its intensity and poignancy is the attitude of the population against contamination threats, both real and hypothetical; the panic and the atmosphere of suspicion are the same, from the Peloponnesian War to the present.

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Supplementary data