From Hammurabi's Code to the Arms Trade Treaty and the Treaty on the Prohibition of Nuclear Weapons, humanitarian rules have continuously evolved as part of efforts to constraint belligerents’ behaviour and provide protection for victims of armed conflicts. Historical analyses of humanitarian rules not only shed light on how wars, hostilities and their limits were conceived throughout history, but can also reinforce the customary nature of these rules.

More than a millennium before Henry Dunant's A Memory of Solferino was published, humanitarian ideas and principles were already present in the discourses and norms of the classical Greeks, and war among Greek city-States was regulated by a corpus of norms common to the Greek people. Emiliano Buis's book, Taming Ares: War, Interstate Law, and Humanitarian Discourse in Classical Greece, is one of the rare books to look at Classical Greece texts and norms from various religious, political, social, literary and artistic sources, through the prism of international humanitarian law (IHL), and offers a fascinating perspective on the historical roots of IHL.

This book allows readers to get an in-depth view into how norms, inter-polity relations and laws common to the classical Greeks were conceived during the Peloponnesian War period (431–404 BCE), and provides an enlightening analysis of some of the precursory roots of what we know today as ius ad bellum and ius in bello. Not only is the book based on meticulous research, but each of its sections is also supported by numerous examples and quotations of the original texts used as reference sources, with their English translation, allowing readers to fully appreciate how the norms and ideas preceding modern-day IHL were expressed.

The first part of the book is dedicated to demonstrating that classical Greek inter-city relations were regulated by norms relating to the legal realm. In the first chapter, Buis introduces what represented the law in the ancient world and argues that this can only be understood when analyzed together with other social regulations such as religious, moral, political and international or inter-polis rules. In the ancient Greeks’ conception of law, the performative aspect of justice, acts of legislation and citizens’ participation were crucial, and are highlighted through the presentation of a shared structural logic between theatre and judicial activities. For instance, in Athens, where judicial functions were not professionalized, justice took the form of oral and public debates, allowing participation of citizens. Performance was a cultural value that allowed both theatre and law to be perceived as dynamic public creations.

In the second chapter, the author explores the notion of international subjectivity at the time of the Greek poleis. He argues that international law may have existed even before the theorization of its “subject”.Footnote ¹ His analysis extends from the domestic regulation of associations in Athens during the fourth and fifth centuries to the Greek city-States’ conception of social groups and associations. In these contexts, the poleis were conceived as not only territories, but also as their people: “For men are the polis, and not walls or the ship empty of men.”Footnote ² To exemplify this, Buis presents a study of various treaties signed during the Peloponnesian War analyzing the denomination of the different parties. Indeed, in many treaties concluded between allies during the period, the texts refer to the people (such as Athenians and Rhegians) and not to the cities (such as Athens or Rhegium), showing that Greeks conceived the representation of their polis as being based on its people, and not as an entity separated from its members. Based on this analysis, Buis suggests that the idea of starting from subjectivity to conceive international law may have existed before the conception of “subjects”, as we know of them today. Indeed, although Greek city-States were not conceived as subjects distinct from their people, they nevertheless concluded treaties and acted as autonomous and, to some extent, sovereign entities.

Buis also illuminates how the notion of the equality of parties was important in inter-polis treaties, along with the concept of reciprocal obligations.Footnote ³ However, much like some contemporaneous treaties, abuses and hegemony of more powerful cities was evidenced in several inter-polis treaties. For instance, in 403 BCE, Sparta, using its privileged position, imposed a treaty obligation on the Athenians to destroy their walls, hand over their fleet and “have the same allies and enemies as the Spartans”.Footnote ⁴ The creation of some international organizations, which for example took the form of religious or military associations, also contributed to the imbalance of power between theoretically equal parties. Indeed, although these associations guaranteed formal equality between city-States, they were in fact controlled by leaders who were entitled to take actions on behalf of the organization.Footnote ⁵ When reading this part of the analysis, one cannot help but reflect on how this aspect of international relations seems to present certain present-day analogues.Footnote ⁶

In the second part of the book, Buis examines the rules pertaining to the conduct of war and its limits in the normative corpus regulating Greek inter-polis relations. He starts by exploring the concept of just war in classical Greece and the grounds it laid for the notion of self-defence. Chapter 3 thus delves into the rhetoric of the use of force used by the ancient Greeks, shedding light on their need to limit military action to cases considered as just. In various sources analyzed by the author, the need to justify war, and to explain its causes through a discourse acceptable both at the political and at the religious levels, is evident. For instance, in Politics, Aristotle (384–322 BCE) presents different legitimate justifications for war, among which defence against aggression by others can be found.Footnote ⁷ Also, in respect to the war between the Corinthians and the Corcyraeans (435–431 BCE), appeals to just war are evidenced in the arguments justifying the actions of one party because of prior harm caused by the other. As part of this discourse, the need to help victims of acts of aggression or of unjust or unfair actions of an enemy who had refused arbitration and insisted on the recourse to arms are both presented as justification for waging war in sources from the time.Footnote ⁸ Through drawing on various sources that present the innumerable justifications offered for military action, the author demonstrates how the notion of self-defence was considered as a valid reason to wage war among the ancient Greeks and was often part of official discourses. Based on references to a right, or a universal law, to defend oneself when one is the victim of an aggression, as well as to a common legal basis on which to build a self-defence discourse, Buis traces a possible source of the contemporary right to self-defence under international law. He further notes that “little progress has been made in terms of ius ad bellum for pragmatically establishing the grounds that would ‘authorize’ armed attacks against those who are identified as enemies”.Footnote ⁹

In the fourth and final chapter, the normative framework surrounding the conduct of hostilities and the limits imposed by inter-polis law is examined. From an IHL point of view, this chapter is probably the most enlightening. It begins with a presentation of how military organizations developed at the time, and how, by the same token, these organizations shaped the formalities surrounding the conduct of war. Parallels can be drawn with the performative aspect of court proceedings or theatre: for the ancient Greeks, the conduct of war could also be perceived as a performance structured by formal and informal rules. The analysis of those rules and their possible affiliation with the ones of contemporary ius in bello compose the bulk of this chapter. For instance, the notion of military necessityFootnote ¹⁰ was present in the discourse of the Greeks and was often used to explain or justify an attack. Thus, when the Athenians turned a Boeotian temple into a fortification and contaminated its sacred water during the Battle of Delium in 424 BCE, they were accused by the latter of acting contrary to the law. They argued that they were compelled to act in this way after the invasion by the Boeotians.Footnote ¹¹

Buis also traces indications of the existence of a principle of distinction between those directly involved in hostilities and the civilian population to the time of the ancient Greeks. He does this through cited sources which stress the need to fight in a defined battlefield in order to avoid widespread violence that could have unjustifiable consequences for the population.Footnote ¹² The protection of envoys and heralds was also recognized during inter-polis wars, and it was considered contrary to the common law of the Greeks to arrest them.Footnote ¹³ Civilians or non-combatants in general also benefited from the protection of some rules. For instance, Thucydides reports that in the treaty between Argos and Sparta, it was established that all captured minors would be returned at the end of hostilities.Footnote ¹⁴ Further, it was contrary to the common law of the Greeks to attack temples and other religious facilities, or to engage in acts of pillage, illicit entry or destruction of these sites.Footnote ¹⁵ Religious celebrations of the enemy were to be respected, and attacks during them were prohibited.

As for prisoners of war, an interesting reference in Xenophon's Life of Agesilaus mentions that prisoners should be treated not as criminals to be punished, but rather as men to be guarded.Footnote ¹⁶ The book also offers some examples of prisoners of war exchanges in ancient GreeceFootnote ¹⁷ and cites a passage from Euripides’ tragedy Children of Heracles, produced c. 403 BCE, suggesting that it was considered contrary to the law to kill a prisoner of war.Footnote ¹⁸ Some sources studied by Buis also mention the importance of having doctors among Greek armies to take care of the wounded.Footnote ¹⁹ The respect and honour due to fallen combatants, including enemy ones, was also part of Panhellenic nomos.Footnote ²⁰

A fourth-century decree from Tralleis granting a right for supplicants to be accepted in the sanctuary of Dionysus suggests that supplicants and those who had surrendered benefited from some protection as well. This is illustrated by Aeschylus’ tragedy The Supplicants (463 BCE), in which fifty women from Egypt, known as the Danaides, fled from a forced marriage with their cousin and sought asylum in Argos. In the play, the issue of whether the women can stay is submitted by the king to an assembly of the people, who vote to accept the women. A decree is passed granting them the status of foreign residents. In this case, the author highlights the similarity between arguments presented by the Danaides to advocate in favour of Argos granting them asylum, and present-day refugee status: having crossed an international border, persecution, non-refoulement and even the absence of commission of crime by the Supplicants.Footnote ²¹

The ancient texts that Buis cites also point to how the classical Greeks imposed limits on the means and methods of warfare. For instance, around 595–585 BCE, after the Amphictyonic League contaminated the Pleistus river with a poisonous plant named hellebore, Aeschines mentions an agreement to prevent such action in the future, suggesting a need to establish norms limiting unnecessary and superfluous suffering.Footnote ²²

A passage from Plato's Republic (c. 380 BCE) illustrates the importance for the Greek people of respecting some limits in warfare. It also contains an original and innovative proposal: that barbarians – i.e., non-Greeks – receive the same treatment as Greeks, venturing the idea that all those not participating in hostilities should always be protected.

In the last part of his book, Buis addresses post-conflict resolution, prosecution and transitional justice. While the author admittedly notes that there have been very few instances of prosecution for acts committed during armed conflicts in classical Greece, he does highlight these thought-provokingly rare cases. One example, found in Xenophon's writings, is the tribunal set up in 405 BCE by the Spartan general Lysander, to judge his enemies, especially the Athenians, who voted that if they were victorious they would cut off the hands of the vanquished. Another case is that of the “Trial of the Generals”, which took place in 406 BCE before the Assembly, rather than before a court. According to Xenophon's writings, the generals were put on trial on the basis of their failure to rescue the shipwrecked, but there are also indications that they were tried for treason. Footnote ²⁴

The most interesting example of post-conflict resolution in ancient Greece put forth by Buis is probably the tribunal established to judge those leaders in positions of power during the four-month Thirty Tyrants reign. This reign ended with the killing of many Athenians and the displacement of about half of the city-State's population. The decision to judge only the main leaders and not everyone involved was praised by Aristotle in The Constitution of the Athenians:

Although it is incontestable that the rules governing classical Greek inter-city conflicts and relations were mainly developed and imposed by the most powerful political entities, and that the rules of armed conflict were – as they still are – subject to political manipulation, it is also evident that some inter-polis values and principles were the basis for several rules of restraint in respect to warfare. Buis's meticulous analysis of various sources, including treaties, decrees, theatre pieces and literature, evidences that the basis of contemporary IHL can find roots in the distant and archaic humanitarian principles and rules of ancient Greece. It also provides a rich background for understanding the legal framework relating to the conduct of hostilities and the use of force at that time, and an excellent reference for a historical perspective on customary ius ad bellum and ius in bello.

In a surprisingly strong manner, the remote legal norms of ancient Greece analyzed by Buis echo many of the contemporary rules of IHL and thus provide a relevant precedent for some current rules of ius ad bellum and ius in bello. The book also offers an occasion to reflect on the origin and nature of the elementary considerations of humanity as a general principle of law, and on the Martens Clause, which, for the first time, made explicit on the pages of a treaty regulating the conduct of hostilities something that may have always have been there – i.e., laws of humanity and the dictates of public conscience.Footnote ²⁶ As Cassese has said: “Clearly, in spite of its ambiguous wording and its undefinable purport, [the Martens Clause] has responded to a deeply felt and widespread demand in the international community: that the requirements of humanity and the pressure of public opinion be duly taken into account when regulating armed conflict.”Footnote ²⁷ Reading Taming Ares is also a journey into the genesis of this “deeply felt and widespread demand”.