Archaeological excavations suggest that druzhinas existed in the region as far back as the 6th and 7th centuries.
Druzhinniks (members of the druzhina) served freely. At any moment any of them could leave one knyaz and join another one. Modern estimates of sizes of a druzhina match that of ibn Fadlan's: sizes varied, but never exceeded several hundred persons. During military campaigns a druzhina was a nucleus of the troops formed by means of a kind of levy.
A druzhina was paid by a knyaz, and received a share of military loot.
In the 11th and 12th centuries the druzhina separates into two layers: elder druzhina (дружина старшая), also called better druzhina (дружина лепшая) or fore druzhina (дружина передняя), and younger druzhina (дружина молодшая). The elder druzhina consisted of knyaz's men (княжие мужи) who eventually became boyars. They held higher military and civil positions (posadnik, Voivode) and were advisors of a knyaz.
In addition to military service, druzhinniks of the younger druzhina (called otroki or gridni) ran errands for a knyaz and served as his bodyguards. Younger druzhina did not take part in knyaz's councils, with the exception of military ones, which had a very broad representation.
Manuscripts mention that elder druzhinniks had their own personal druzhinas.
When a knyaz died, his druzhina was inherited by his successor, who usually already had his own druzhina. This was usually a source of rivalry: the druzhina of the previous knyaz claimed experience, while the newcomers commanded the trust of the new leader.
Starting in the 12th century in northern principalities, a land-endowed military class had formed from druzhina.