See Waller, A. L., Feud: Hatfields, McCoys, and Social Change in Appalachia, 1860-1900 (1988).
Up to the early modern period, feuds were considered legitimate legal instruments and were regulated to some degree. Once states asserted and enforced a monopoly on legitimate use of force, feuds became illegal and the concept acquired its current negative connotation.
Originally, a vendetta was a blood feud between two families where kinsmen of the victim intended to avenge his or her death by killing either those responsible for the killing or some of their relatives. The responsibility to maintain the vendetta usually falls on the closest male relative to whoever has been killed or wronged, but other members of the family may take the mantle as well. If the culprit had disappeared or was already dead, the vengeance could extend to other relatives.
Vendetta is typical of societies with a weak rule of law (or where the state doesn't consider itself responsible for mediating this kind of dispute) where family and kinship ties are the main source of authority. An entire family is considered responsible for whatever one of them has done. Sometimes even two separate branches of the same family could come to blows over some matter.
The practice has mostly disappeared with more centralized, rationalistic societies where law enforcement and criminal law take responsibility of punishing lawbreakers.
In ancient Homeric Greece, the practice of personal vengeance against wrongdoers was considered natural and customary: "Embedded in the Greek morality of retaliation is the right of vendetta . . . Vendetta is a war, just as war is an indefinite series of vendettas; and such acts of vengeance are sanctioned by the gods".
In the ancient tribal Hebraic context, it was considered the duty of the individual and family to avenge evil on behalf of God. The executor of the law of blood-revenge who personally put the initial aggressive killer to death was given a special designation: go'el haddam, the blood-avenger or blood-redeemer (Num. 35: 19, etc.). Six cities of refuge were established to provide a "cooling off" phase as well as due process for the accused. As the Oxford Companion to the Bible states: "Since life was viewed as sacred (Gen. 9.6), no amount of blood money could be given as recompense for the loss of the life of an innocent person; it had to be 'life for life'" (Exod. 21.23; Deut. 19.21)".
The Celtic phenomenon of the blood feud demanded "an eye for an eye," and usually descended into murder. Disagreements between clans might last for generations in Scotland and Ireland. Due to the Celtic heritage of many whites living in Appalachia, a series of prolonged violent engagements in late- nineteenth-century Kentucky and West Virginia were referred to commonly as feuds, a tendency that was partly due to the nineteenth-century popularity of William Shakespeare and Sir Walter Scott, authors who both wrote semihistorical accounts of blood feuds. These incidents, the most famous of which was the Hatfield-McCoy feud, were regularly featured in the newspapers of the eastern U.S. between the 1880s and the early twentieth century. Although they were interpreted as such at the time, there is little reason to believe that these American incidents had any correlation to "feuding" in Europe centuries earlier.
The Central Asian plateau (north of China) at the time of Genghis Khan's youth was divided into several nomadic tribes or confederations—among them Naimans, Merkits, Uyghurs, Tatars, Mongols, and Keraits—that were all prominent in their own right and often unfriendly toward each other, as evidenced by frequent raids, revenges, and plundering.
In Japan's feudal past the Samurai class upheld the honor of their family, clan, or their lord by katakiuchi (敵討ち), or revenge killings. These killings could also involve the relatives of an offender. While some vendettas were punished by the government, such as that of the 47 Ronin, others were given official permission with specific targets.
At the Reichstag at Worms in 1495 the right of waging feuds was abolished. The Imperial Reform proclaimed an "eternal public peace" (Ewiger Landfriede) to put an end to the abounding feuds and the anarchy of the robber barons and it defined a new standing imperial army to enforce that peace. However, it took a few more decades until the new regulation was universally accepted. In 1506, for example, knight Jan Kopidlansky killed somebody in Prague and the Town Councillors sentenced him to death and had him executed. Brother Jiri Kopidlansky revenged himself by continuing atrocities.
More than a third of the Ya̧nomamö males, on average, died from warfare. The accounts of missionaries to the area have recounted constant infighting in the tribes for women or prestige, and evidence of continuous warfare for the enslavement of neighboring tribes such as the Macu before the arrival of European settlers and government.
The Clan Gordon was at one point one of the most powerful clans in middle Scotland. Clan feuds and battles were frequent, especially with the Clan Cameron, Clan Murray, Clan Forbes, and the Chattan Confederation.
In Corsica, vendetta was a social code that required Corsicans to kill anyone who wronged the family honor. It has been estimated that between 1683 and 1715, nearly 30,000 out of 120,000 Corsicans lost their lives to vendetta.
Throughout history, the Maniots—one of Greece's toughest populations—have been known by their neighbors and their enemies as fearless warriors who practice blood feuds. Some vendettas went on for months and sometimes years. The families involved would lock themselves in their towers and when they got the chance would murder members of the opposing family.
The Basque Country in the Late Middle Ages was ravaged by bitter partisan wars between local ruling families. In Navarre, these conflicts became polarised in a violent struggle between the Agramont and Beaumont parties. In Biscay, the two major warring factions were named Oinaz and Gamboa. (Cf. the Guelphs and Ghibellines in Italy). High defensive structures ("towers") built by local noble families, few of which survive today, were frequently razed by fires, sometimes by royal decree.
Leontiy Lyulye, an expert on conditions in the Caucasus, wrote in the mid-19th century: "Among the mountain people the blood feud is not an uncontrollable permanent feeling such as the vendetta is among the Corsicans. It is more like an obligation imposed by the public opinion." In the Dagestani aul Kadar, one such blood feud between two antagonistic clans lasted for nearly 260 years, from the 17th century till the 1860s.
An alternative to feud was blood money (or weregild in the Norse culture), which demanded payment of some kind from those responsible for a wrongful death (even an accidental one). If these payments were not made or were refused by the offended party, a blood feud would ensue.
Mutual vendetta may develop into a vicious circle of further killings, retaliation, counterattacks, and all-out warfare that can end in the mutual extinction of both families. Often the original cause is forgotten, and feuds continue simply because it is perceived that there has always been a feud.
There is a scene in The Godfather, in which Michael Corleone, hiding from U.S. police in Sicily, walks through a village with his two bodyguards. Michael asks, "Where are all the men?" The bodyguard replies, "They're all dead from vendettas."
In modern hip-hop, rappers notoriously engage in verbal warfare with one another, which occasionally spills over into actual violence and sometimes murder. The most high-profile feud in rap was the Tupac - Notorious BIG Feud, which included several shootings and attacks on friends of both icons. It culminated with the highly publicized killings of Tupac Shakur in 1996 and The Notorious BIG in 1997. A list of all feuds can be found on CelebrityFeuds.com Other notable rap feuds have included: