In the first century BC, Lucretius mused that early humans may have attempted to launch wild beasts, such as lions or "savage boars," against the enemy, but with catastrophic results. War pigs are pigs reported to have been used in ancient warfare as a countermeasure against war elephants. According to legend recounted in the "Alexander Romance" by Pseudo-Callisthenes, Alexander the Great learned about this "secret weapon" against war elephants from Porus in India.

Pliny the Elder reported that "elephants are scared by the smallest squeal of the hog".Aelian confirmed that elephants were frightened by squealing pigs (and rams with horns), and reported that the Romans exploited squealing pigs (and rams) to repel the war elephants of Pyrrhus in 275 BC. Procopius, in History of the Wars, records that the defenders of Edessa suspended a squealing pig from the walls to frighten away Khosrau's single siege elephant in the sixth century AD.

Historical accounts of incendiary pigs or flaming pigs were recorded by the military writer Polyaenus and by Aelian. Both writers reported that Antigonus II Gonatas' siege of Megara in 266 BC was broken when the Megarians doused some pigs with combustible pitch or resin, set them alight, and drove them towards the enemy's massed war elephants. The elephants bolted in terror from the flaming, squealing pigs, often killing great numbers of their own soldiers.

War is an organized, armed, and often a prolonged conflict that is carried on between states, nations, or other parties typified by extreme aggression, social disruption, and usually high mortality. War should be understood as an actual, intentional and widespread armed conflict between political communities, and therefore is defined as a form of political violence. The set of techniques used by a group to carry out war is known as warfare. An absence of war (and other violence) is usually called peace.

In 2003, Nobel Laureate Richard E. Smalley identified war as the sixth (of ten) biggest problems facing the society of mankind for the next fifty years. In the 1832 treatise On War, Prussian military general and theoretician Carl von Clausewitz defined war as follows: "War is thus an act of force to compel our enemy to do our will."

While some scholars see warfare as an inescapable and integral aspect of human culture, others argue that it is only inevitable under certain socio-cultural or ecological circumstances. Some scholars argue that the practice of war is not linked to any single type of political organization or society. Rather, as discussed by John Keegan in his History of Warfare, war is a universal phenomenon whose form and scope is defined by the society that wages it. Another argument suggests that since there are human societies in which warfare does not exist, humans may not be naturally disposed for warfare, which emerges under particular circumstances. The ever changing technologies and potentials of war extend along a historical continuum. At the one end lies the endemic warfare of the Paleolithic^{[citation needed]} with its stones and clubs, and the naturally limited loss of life associated with the use of such weapons. Found at the other end of this continuum is nuclear warfare, along with the recently developed possible outcome of its use, namely the potential risk of the complete extinction of the human species.

A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives. Pigs are omnivores and are highly social and intelligent animals.^{[citation needed]}

A typical pig has a large head with a long snout which is strengthened by a special prenasal bone and by a disk of cartilage at the tip. The snout is used to dig into the soil to find food and is a very acute sense organ. There are four hoofed toes on each foot, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.

The dental formula of adult pigs is Failed to parse (Missing texvc executable; please see math/README to configure.): \tfrac{ 3.1.4.3}{ 3.1.4.3} , giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male the canine teeth form tusks, which grow continuously and are sharpened by constantly being ground against each other.

With around 1 billion individuals alive at any time, the domesticated pig is one of the most numerous large mammals on the planet.