The term, equated to Ivan IV's domestic policy, is now remembered mainly for the notorious organization of the Oprichniks, based in this territory, which terrorized its population and especially decimated the city of Novgorod, and as the name of the period in Russian history when they operated.
Tsar Ivan began to suspect that other aristocrats were also ready to betray him. On the third of December, 1564, Tsar Ivan left Moscow, carrying all of its religious and historical relics with him in his entourage, for the neighboring suburb of Alexandrov. The church, unable to do anything but gawk astonished, begged the tsar to return to Moscow. In 1565, the officials of the church met with Ivan and consented to his creation of the Oprichnina in exchange for his return to Moscow.
That same year, Ivan formed the Oprichnina, which gave him a section of territory (mainly the Northeast). There were few large landowners; the area was dominated by service nobility and state peasantry. In the territory of the Oprichnina he could be free from the interference of the powerful feudal aristocracy and rule as a completely unlimited autocrat.
This whole system of the Oprichnina has been viewed by some historians as a tool against the powerful hereditary nobility of Russia (boyars) who opposed the trend toward centralization.
The Oprichnina was treated very similarly to the church at the time, enjoying the same freedom from taxes and monastic organization (with the tsar himself as abbot). The main difference between the two was that, instead of being a religious body, the oprichnina was exclusively Ivan's means of carrying out his will.
The Oprichnina was administered by the oprichniks, who used extreme violence against any opposition to Ivan's rule. This included both nobles and peasants, with many of the oprichniks being members of the elite. The oprichniki were described as "trusties of Ivan who wore black cowls and carried brooms and dogs' heads at their saddle-bows" .
During the era of the Oprichnina, oprichniks killed thousands and devastated the area. For example, in 1570 Ivan's concern at the strategic value of the city in the war with the Teutonic Order and Sweden led him to order the sacking of Novgorod. The oprichniks plundered the city in response and by some accounts killed as many as 30,000 of its inhabitants .
Many modern researchers estimate the number of victims to be between two and three thousand. (After the famine and epidemics of 1560s the population of Novgorod did not exceed 10,000-20,000.)
The Oprichniks would be dressed in black and rode black horses. The saddle pommels were emblazoned with a dog's head and a broom, signifying the hounding and sweeping of treason from the realm.
In the 1560s the combination of the very poor harvests (the period called the little ice age), the plague, Polish-Lithuanian raids, Tatar attacks, and the sea-trading blockade carried out by the Swedes, Poles and the Hanseatic League devastated Russia.
The oprichnina did nothing to help reverse these effects, perhaps even helping to undermine Russia's stability. What had once been Russia's best and most fertile areas had been devastated and had fallen well below the rest of the country. In fact, the price of grain increased by a factor of ten. Many people living within the Oprichnina even fled to other regions.
Under these circumstances the existence of the two systems of authority (Oprichnina and Zemshchina) and the struggle against aristocracy added to the economic and political disorganization of the country.
The Oprichnina had been total failure and Ivan was forced to disband it in autumn of 1572. Whether the Oprichnina had benefitted Russia at all was questioned by many; tax revenues had not increased as the tsar had hoped, and Russia quickly lost all of its gains in the war for Livonia.
Although the Oprichnina was successful in instilling a fearfully submissive view towards the Tsar in Russians across the kingdom, it ultimately posed as no tangible improvement if not a detriment to the economy and stability of Russia.
In turn, Tchaikovsky's opera inspired a 1911 painting by Apollinary Vasnetsov, depicting a city street and people fleeing in panic at the arrival of the Oprichniks.
Years after the reign of Ivan the Terrible, the oprichnina continued to affect Russia. Stalin, himself, based many of his own purging schemes on the 'terrible, blood thirsty' Oprichnina, and the position of tsar was forever after shrouded with a great sense of terrifying power.
Sergei Eisenstein depicted the oprichniki as healthy, loyal, clean-looking persons in the movie Ivan The Terrible, Part I and then proceeded to show them in a less flattering light in Ivan The Terrible, Part II.