Sviatoslav I of Kiev in the context of "Pereyaslavets"

From c. 970 until 1018, a series of conflicts between the Bulgarian Empire and the Byzantine Empire led to the gradual reconquest of Bulgaria by the Byzantines, who thus re-established their control over the entire Balkan peninsula for the first time since the 7th-century Slavic invasions. The struggle began with the incorporation of eastern Bulgaria after the Russo-Byzantine War (970–971). Bulgarian resistance was led by the Cometopuli brothers, who – based in the unconquered western regions of the Bulgarian Empire – led it until its fall under Byzantine rule in 1018.

As the Byzantine-Bulgarian relations deteriorated by the end of the 960s, the Eastern Roman Empire paid the Kievan prince Sviatoslav to attack Bulgaria. The unexpected collapse of Bulgaria and Sviatoslav's ambitions to seize Constantinople caught the Eastern Roman Empire off-guard but they managed to pull back the Kievan armies and occupied eastern Bulgaria including the capital Preslav in 971. Emperor Boris II was captured and taken to Constantinople where he abdicated and the Byzantine Emperor John I Tzimiskes announced the annexation of Bulgaria, even though the Eastern Roman Empire only controlled Eastern Bulgaria at the time, and the lands to the west remained under Bulgarian control. The four brothers David, Moses, Aron, and Samuel of the Cometopuli dynasty ruled in the free territories and in 976, launched a major offensive against the Byzantines to regain the lost lands. Soon, the youngest brother, Samuel, took complete authority following the deaths of his three eldest brothers.

The Caspian expeditions of the Rus' were military raids undertaken by the Rus' between the late 9th century and c. 1041 on the Caspian Sea shores, of what are nowadays Iran, Dagestan, and Azerbaijan. Initially, the Rus' appeared in Serkland in the 9th century travelling as merchants along the Volga trade route, selling furs, honey, and slaves. The first small-scale Viking raids took place in the late 9th and early 10th century. The Rus' undertook the first large-scale expedition in 913; having arrived on 500 ships, they pillaged in the Gorgan region, in the territory of present-day Iran, and more to the west, in Gilan and Mazandaran, taking slaves and goods. On their return, the northern raiders were attacked and defeated by the Khazars in the Volga Delta, and those who escaped were killed by the local tribes in the middle Volga.

During their next expedition in 943, the Rus' captured Bardha'a, the capital of Arran, in the modern-day Republic of Azerbaijan. The Rus' stayed there for several months, killing many inhabitants of the city and amassing substantial plunder. It was only an outbreak of dysentery among the Rus' that forced them to depart with their spoils. Sviatoslav, prince of Kiev, commanded the next attack, which destroyed the Khazar state in 965. Sviatoslav's campaign established the Rus's hold on the north-south trade routes, helping to alter the demographics of the region. Raids continued through the time period with the last Scandinavian attempt to reestablish the route to the Caspian Sea taking place in c. 1041 by Ingvar the Far-Travelled.

Sviatoslav's invasion of Bulgaria was a conflict beginning in 967/968 and ending in 971, carried out in the eastern Balkans, and involving the Kievan Rus', Bulgaria, and the Byzantine Empire. The Byzantines encouraged the Rus' ruler Sviatoslav to attack Bulgaria, leading to the defeat of the Bulgarian forces and the occupation of the northern and north-eastern part of the country by the Rus' for the following two years. The allies then turned against each other, and the ensuing military confrontation ended with a Byzantine victory. The Rus' withdrew and eastern Bulgaria was incorporated into the Byzantine Empire.

In 927, a peace treaty had been signed between Bulgaria and Byzantium, ending many years of warfare and establishing forty years of peace. Both states prospered during this interlude, but the balance of power gradually shifted in favour of the Byzantines, who made great territorial gains against the Abbasid Caliphate in the east and formed a web of alliances surrounding Bulgaria. By 965/966, the warlike new Byzantine emperor Nikephoros II Phokas refused to renew the annual tribute that was part of the peace agreement and declared war on Bulgaria. Preoccupied with his campaigns in the East, Nikephoros resolved to fight the war by proxy and invited the Rus' ruler Sviatoslav to invade Bulgaria.

Oleg Sviatoslavich (Олег Святославич; died 977) was the prince of the Drevlians from 970 until his death in 977. He was the second son of Sviatoslav I of Kiev of the Rurik dynasty.

Olga (Church Slavonic: Ольга; Old Norse: Helga; c. 890–925 – 11 July 969) was a regent of Kievan Rus' for her son Sviatoslav from 945 until 957. Following her baptism, Olga took the name Elenа. She is known for her subjugation of the Drevlians, a tribe that had killed her husband Igor. Even though it was her grandson Vladimir who adopted Christianity and made it the state religion, she was the first ruler to be baptized.

Olga is venerated as a saint in the Eastern Orthodox Church with the epithet "Equal to the Apostles". Her feast day is 11 July.

Malusha Malkovna (Old East Slavic: Малушa) was allegedly a servant (kholopka) for Olga of Kiev and a concubine of Sviatoslav I of Kiev. According to chronicles, she was the mother of Vladimir the Great and sister of Dobrynya. The Norse sagas describe Vladimir's mother as a prophetess who lived to the age of 100 and was brought from her cave to the palace to predict the future.