John I Tzimiskes in the context of "Byzantine–Bulgarian wars"

Constantine VIII (Greek: Κωνσταντῖνος, romanized: Kōnstantīnos; 960 – 11/12 November 1028) was de jure Byzantine emperor from 962 until his death. He was the younger son of Emperor Romanos II and Empress Theophano. He was nominal co-emperor from 962, successively with his father; stepfather, Nikephoros II Phokas; uncle, John I Tzimiskes; and brother, Basil II. Basil's death in 1025 left Constantine as the sole emperor. He occupied the throne for 66 years in total, making him de jure the longest-reigning amongst all Roman emperors since Augustus.

Constantine displayed a lifelong lack of interest in politics, statecraft and the military, and during his brief sole reign the government of the Byzantine Empire suffered from mismanagement and neglect. He had no sons and was instead succeeded by Romanos Argyros, husband of his daughter Zoe.

Basil Lekapenos (Greek: Βασίλειος Λεκαπηνός, romanized: Basíleios Lekapēnós; c. 925 – c. 985), also called the Parakoimomenos (ὁ παρακοιμώμενος) or the Nothos (ὁ Νόθος, "the Bastard"), was an illegitimate child of the Byzantine emperor Romanos I Lekapenos. He served as the grand chamberlain and chief minister of the Byzantine Empire for most of the period 947 to 985, under emperors Constantine VII (his brother-in-law), Romanos II (his nephew), Nikephoros II Phokas, John I Tzimiskes, and Basil II (his great nephew).

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.

Paristrion (Greek: Παρίστριον, lit. 'beside the Ister'), or Paradounabon/Paradounabis (Παραδούναβον / Παραδούναβις), which is preferred in official documents, was a Byzantine province covering the southern bank of the Lower Danube (Moesia Inferior) in the 11th and 12th centuries.

Although Byzantine authors use the term to describe the lands along the Danube in general, the province of Paristrion seems to have comprised mostly modern Dobruja. It is not certain exactly when the province was established: the Romanian scholar Nicolae Bănescu considered that it was established immediately after the end of the Rus'–Byzantine War of 970–971, while others, such as Vasil Zlatarski, thought it a later, mid-11th century creation. It was governed by a katepano or a doux, and was probably based at Dorostolon (modern Silistra), where a Byzantine strategia ("generalcy") is indeed attested in the 970s. In the aftermath of his victory over the Rus', Emperor John I Tzimiskes (r. 969–976) appointed general Leo Sarakenopoulos as commander over north-eastern Bulgaria, based at Pereyaslavets/Ioannopolis. Sarakenopoulos and his subordinates engaged in major fortification activities in the region of the Dobruja over the next few years, where abandoned Roman-era forts were rebuilt and re-occupied.

The Theme of Bulgaria (Greek: Θέμα Βουλγαρίας, romanized: Thema Boulgarias) was a theme (province) of the Byzantine Empire established by Emperor Basil II after the conquest of Bulgaria in 1018. Its capital was Skopje and it was governed by a strategos. The theme of Bulgaria did not encompass the old Bulgarian lands between the Haimos Mountains and the river Danube, that included the former capitals Pliska and Preslav. This territory was administered independently and was considered as autonomous military unit, designated as Paristrion or Paradunavon, meaning the "lands beside the Danube".

The local inhabitants were called Bulgarians, but some authors maintain this name did not have an ethnic meaning. Bulgaroi was a political name, in the same way as Romaioi. The emotive force which the name has today is quite distinct from that which inspired the emperors John I and Basil II to celebrate their victories with elaborate ceremony. Their achievement was to restore the empire to her ancient limits, and eliminate the rival, distinct, independent empire that had emerged from the Byzantine model and had been established and recognized within those limits. It can be seen from the fact that the rebels in the Uprising of 1072 invited a Serbian king from Diokleia Constantine Bodin, which belonged to the former empires of Simeon I of Bulgaria and Samuel of Bulgaria, to be the Tsar of the Bulgarians. However, some authors suggest that Bodin was invited, because he was the great-great-grandson of Samuel of Bulgaria.