And to seal his prayer, farseeing Zeus sent down a sign.

He launched two eagles soaring high from a mountain ridge

...All were dumbstruck, watching the eagles trail from sight,

people brooding, deeply, what might come to pass...

Until the old warrior Halitherses,

Master's son, broke the silence for them:

the one who outperformed all men of his time

at reading bird-signs, sounding out the omens,

rose and spoke, distraught for each man there

– Homer, The Odyssey, 8th century BC.

Uncertainty is embedded in the practice of warfare. The potential rewards can be great, yet the cost of failure is incalculably grave. While war is a cooperative endeavor, often undertaken to benefit a larger social group, wars are fought by individual people with their own interests and motivations. The instinct of self-preservation, the anticipation of potentially disastrous consequences, and extreme feelings of fear may act as constraints on the engagement of aggressive conflict. To mitigate these limitations, cultures developed beliefs and practices to reduce the fear of warriors, and increase their willingness to fight on behalf of the group. Many such traditions purport to offer nothing less than protection and approval from the gods themselves.

Societies throughout history have always played close attention to the clues offered by the divine. As archaeologist Bruce Trigger notes in his cross-cultural study of the kingdoms of ancient Egypt, Mesopotamia, Shang China, the Aztecs, Maya, Inca, and the Yoruba: “Ascertaining the will of the gods through reading omens and practicing divination was highly elaborated in all the early civilizations.” The ubiquity of these beliefs and practices, and their association with powerful and long-lasting regimes, hints towards a functional component, particularly in the domain of warfare.

Rituals play an important role in warfare across numerous societies, as anthropologist Luke Glowacki notes in a recent commentary on the cultural evolution of war rituals. Glowacki writes that,

Although cultural systems contribute to incentivizing participation [in warfare] (Glowacki & Wrangham 2013; Zefferman & Mathew 2015), humans also adopt superstitious beliefs and behaviors to overcome anxiety and fear and increase self-confidence. Warriors in numerous societies carry amulets or use drugs and alcohol to mitigate fear (Goldschmidt 1994). With astonishing frequency, many of these interventions purport to make enemies unable to see or harm the warrior.

Importantly, such beliefs and practices can reduce the perceived cost of engaging in warfare. If you believe you cannot be harmed by conventional means you may be less hesitant about participating in a raid on a rival group.

Related to the practice of rituals that reduce fear, omens and prophecy can fulfill a similar function. The uncertainty of conflict is reduced substantially if one can foretell the outcome. Across many societies, dreams, the movement of animals, the position of stars, and the proclamations of prophets were believed to offer tantalizing hints of a momentous future.

Anthropologist George Murdock, who helped compile many of the large cross-cultural databases still in use today, such as the Ethnographic Atlas and the Standard Cross-Cultural Sample, provides multiple examples across societies where omens and visions had an important role in the practice of warfare. Murdock writes that in native Samoa, before battle:

A feast is held, and the village gods are consulted by divination. If the auspices seem favorable, the war party starts out; it returns immediately, however, if any bad omen, like the squeaking of rats, is observed... By observing the behavior of the animal incarnations of the war gods, the success or failure of a military expedition can be predicted. If, for example, an owl, heron, kingfisher, or other fetish bird of a war god flies ahead of an advancing party, it is an omen of victory; if, however, it flies across the path or toward the rear, it is a bad omen, and the party immediately retreats (Murdock 81).

Often, the insight of specialized professionals is required to interpret or act on an omen. Among the Crow American Indians, Murdock writes that, “Any man may organize a war party. But he must first have a vision, or else purchase medicine and receive the details of a vision from a war shaman”. Murdock also notes that among the Haida hunter-fisher-gatherers of British Colombia, a shaman would always accompany war expeditions to read omens.

A ritual or divinatory specialist who plays a prominent role in preparing for battle is found in many societies. Anthropologists Mathies Osterle and Michael Bollig write of the importance of prophets in war planning among Pokot pastoralists of Kenya, “Before the men congregate in a huge final ritual (kokwö luk)…[they] consult a prophet (werkoyon), a ritual specialist who forecasts future events on the basis of his dreams. Only if his visions for the attack are promising will the raid go ahead.”

Among the Mursi pastoralists of Ethiopia, men with divinatory skills examine the intestines of a stock animal to predict the location and severity of future battles. Like the Samoan societies mentioned above, the flight patterns of specific birds are believed to convey information about upcoming battles. Anthropologist David Turton writes;

It is a common occurrence during the dry season for warnings to be sent to the cattle camps from the Omo by older men who “know about birds”, warnings which certainly have the effect of increasing the vigilance of the herders, and, in particular, of persuading them to engage in the irksome and generally unpopular task of scouting in the Mago Valley.