The current study analyzed the data on the presence of foreign military contingents and troops in the Balkans during the late 9th – mid-11th centuries. Particular attention is paid both to the information available in the written sources and to the material evidence (elements of armament) that prove to some extent the existence of military elements ‘external’ to Byzantium and the First Bulgarian Kingdom. The period under consideration was extremely dynamic in terms of military campaigns raids and mercenary activities in the lands along the Lower Danube. From the end of the 9th to the beginning of the 10th century the so-called late nomads, or more specifically Magyars and Pechenegs, began to cross south of the Danube. Some of them were used as mercenaries. The study also sheds light on the presence of troops and mercenaries from Northern Europe in the Balkan territories. In the second half of the 10th century, the Balkans became the object of raids mainly by the Varyago-Russians. It is about the campaigns of the Kievan prince Svetoslav I Igorevich (963 – 972) in the period 968 – 971 to the Bulgarian lands and Constantinople under the rule of the Byzantine emperor John Tzimiskes (969 – 976). A little more than a decade later, after the Christianisation of Kievan Rus in 988, Emperor Basil II (976 – 1025) recruited about 6,000 Varangians to form his guards and thus created the so-called ‘Varangian Corps’, personally responsible for guarding the Byzantine Emperor. Discoveries of northern European origin weaponry in the Balkans are associated with well-armed military contingents from the North and trade relations between the Varangians and Byzantium, which are also well-attested in Byzantine written sources. The study also traces the events and analyses the data (written and material) that we have about the massive late nomadic raids in the 11th century in the lands of the Lower Danube.